The next step was to ascertain whether the disease could be contracted in any other way than by the bites of infected mosquitoes. A camp named Camp Lazear was established and the following tests made: A mosquito-proof building of one room was completely divided by a wire screen from floor to ceiling. In one room fifteen mosquitoes that had previously bitten yellow fever patients and had undergone the proper period of incubation were liberated. In this room a non-immune exposed himself so that he was bitten by several of the insects. A little later the same day and again the next day the mosquitoes were allowed to feed on him for a few minutes. Five days later, the usual incubation period, he developed yellow fever.

At the same time that he entered the building two other non-immunes entered the other compartment where they slept for eighteen nights separated from the mosquitoes by the wire screen. They showed no signs of taking the fever.

In another mosquito-proof house two soldiers and a surgeon, all non-immunes, lived for twenty-one days. From time to time they were supplied with soiled articles of bedding, clothing, etc., direct from the yellow fever hospital in the city. These articles had been soiled by the urine, fecal matter and black vomit obtained from fatal and other cases of yellow fever. These articles were handled and shaken daily, but no disease developed among the men and at the end of the twenty-one days, two other non-immunes relieved them and handled a new supply of clothing in the same way, sleeping between the same sheets that had been used by a patient dying of yellow fever and exposing themselves in every possible way to the soiled clothing. But no disease developed. That these men were susceptible was shown later by inoculating some of them, when they developed the disease.

In another experiment certain men in a camp allowed themselves to be bitten by mosquitoes that had passed through the proper period of incubation and every one of them and no others contracted the disease. It was also shown that a mosquito was capable of communicating the disease as long as fifty-seven days after it had bitten a yellow fever patient. Another set of experiments showed that a subcutaneous injection into a non-immune of a very small quantity of blood from the veins of a yellow fever patient in the first two or three days of the disease would produce the fever.

SUMMARY OF RESULTS

Since that time much other work has been done by independent workers as well as by French and English Commissions both working at Rio de Janeiro. The results of their investigation are practically the same and may be summed up as follows:

1. The virus of the yellow fever is in the blood-plasma, not in the corpuscles, for these may be removed and the plasma still be infective.

2. The virus is conveyed from one patient to another by the yellow fever mosquito, Stegomyia calopus, and in no other way except by experimental injections.

3. The patient is a source of infection only during the first three or four days of the disease (this after the three to six days of incubation).

4. The virus must undergo an incubation period of twelve to fourteen days in the mosquito before she is capable of transmitting the disease.

5. The parasite, whatever it is, has never been seen. It is probably too small to be seen by any of our present microscopes, even the recently invented ultramicroscope. It is probably not a bacterial parasite but very likely a Protozoan, and certain specialists have even shown by the study of all the available data that it almost certainly belongs to the Sporozoan genus Spirocheta.

Now what does all this mean? It means the saving of hundreds of human lives annually. It means the banishing from many localities and possibly very soon from the face of the earth of a disease that since the earliest settlements on this continent has been a source of terror. It means the making habitable of certain places which heretofore a white man has entered only at the risk of his life. It means that quarantines need no longer be established when yellow fever breaks out in a district; quarantines which have inevitably caused the loss of millions of dollars to the world of commerce.

RESULTS IN HAVANA

The first practical work based on these findings was done in Havana. The Yellow Fever Commission made their recommendations in 1900. In 1901 and 1902 they were put into effect. The following table of the death rate there during a period of ten years shows graphically the results:

DEATHS IN HAVANA FROM YELLOW FEVER

- 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 - Jan. 15 7 15 10 69 7 1 8 7 0 Feb. 6 4 4 7 24 1 0 9 5 0 Mar. 4 2 2 3 30 2 1 4 1 0 Apr. 8 4 6 14 71 1 2 0 0 0 May 23 16 10 27 88 4 0 2 0 0 June 69 31 16 46 174 3 1 8 0 0 July 118 77 88 116 168 16 2 30 1 0 Aug. 100 73 120 262 102 16 13 49 2 0 Sep. 68 76 135 166 56 34 18 52 2 0 Oct. 46 40 102 240 42 26 25 74 0 0 Nov. 28 23 35 244 26 13 18 54 0 0 Dec. 11 29 20 147 8 13 22 20 0 0 -

As long as the United States held control at Havana the yellow fever was kept in check by fighting the mosquitoes, when this vigilance was relaxed the fever began to appear again and the Cubans found that it was necessary to keep up the fight against the mosquitoes if the island was to be kept free from the disease.

THE FIGHT IN NEW ORLEANS

In the summer of 1905 came another opportunity to put the knowledge gained during these experiments to a practical test. Samuel Hopkins Adams in his article in McClure's Magazine, June, 1906, says of the beginning of this fight:

"Eight years before, the mosquito-plague had infected the great, busy, joyous metropolis of the south. Ignorant of the real processes of the infection, New Orleans had fought it blindly, frantically, in an agony of panic, and when at last the frost put an end to the helpless city's plight, she lay spent and prostrate. The yellow fever of 1905 came with a more formidable and unexpected suddenness than that of 1897. It sprang into life like a secret and armed uprising in the midst of the city, full-fledged and terrible. But there arose against it the trained fighting line of scientific knowledge. Accepting, with a fine courage of faith that most important preventive discovery since vaccination, the mosquito dogma, the Crescent City marshaled her defenses. This time there was no panic, no mob-rule of terrified thousands, no mad rushing from stunned inertia to wildly impractical action; but instead the enlistment of the whole city in an army of sanitation. Every citizen became a soldier of the public health. And when, long before the plague-killing frost came, the battle was over, New Orleans had triumphed not only in the most brilliant hygienic victory ever achieved in America, but in a principle for which the whole nation owes her a debt of gratitude."

For some time the authorities had been trying to keep secret the fact that the disease was prevalent, but the rapidity with which it spread made them realize that only united action on the part of all the community would be of any avail. The Citizens Volunteer Ward Organizations were organized for the purpose of fighting the mosquitoes which were everywhere. To many the fight looked hopeless. The miles of open gutters, the thousands of cisterns and little pools of standing water everywhere furnished abundant breeding-places for the mosquitoes. The ditches and ponds were drained or salted, the cisterns were screened, infected houses were fumigated, yet the fever continued to spread. Rains refilled the ditches, winds tore the screens from the cisterns, the ignorant people of the French quarter refused to cooeperate. At last the city in desperation appealed to the President for aid. Surgeon J.H. White and a number of officers and men of the United States Public Health and Marine Hospital Service soon took charge of the work. This was continued along the same lines as before with the same object in view. But with the coming of the regulars the work was more systematically and thoroughly done. Every case of fever was treated as though it was yellow fever and every precaution taken to prevent mosquitoes from biting such a patient. The houses in which the fever occurred were thoroughly fumigated to kill any mosquitoes that might be there, and the neighborhood was thoroughly searched to find any places where the mosquitoes might be breeding. So confident were the authorities that the mosquito was the sole cause of the disease spreading, that besides fighting it no other work was undertaken save to make the sick as comfortable as possible.

Finally the results began to be apparent. The number of cases gradually diminished, until long before frost came the city was free from the great pest. Yellow fever will doubtless appear from time to time in New Orleans and other cities, but there is, at least there should be, small danger of another great epidemic, for the people now know how the disease is caused and the remedy.

Not long since I had occasion to write to a prominent entomologist in Louisiana for some specimens of the yellow fever mosquito for laboratory work. The following extract from his reply will show something of the work that is still being done there.

"I am afraid we cannot furnish specimens of Stegomyia, in spite of the fact that Louisiana is supposed to be the most favorable home of this species in the South. Since the light occurrence of yellow fever in this State in 1905, a very vigorous war has been kept up against Stegomyia, and the ordinances of all Louisiana cities and principal towns require the draining of all breeding places of this mosquito and the constant oiling or screening of all cisterns or other water containers. The result is this species is very rare. Here in Baton Rouge I only see one once in a great while, and it would require perhaps a good many days' work at the present season to get as good specimens and as many of them as you require."

IN THE PANAMA CANAL ZONE

Yellow fever was one of the worst obstacles that confronted the French when they were attempting to build the Panama Canal. The story of the suffering and death from this dread disease there is most pathetic. Ship-load after ship-load of laborers were sent over, as those who had gone earlier succumbed to the fever. The contractors were responsible for their men while they were sick and in order to avoid having to pay hospital expenses the men were often discharged as soon as they showed signs of sickness. Many of them died along the roadside while endeavoring to reach some place where they could obtain aid. The hospitals were usually filled with yellow fever patients, a very large percentage of whom died.

Not only the day laborers suffered but many of the engineers, doctors, nurses and others sickened and died of the disease. It is reported that eighteen young French engineers came over on one vessel and in a month after their arrival all but one had died of the yellow fever. Out of thirty-six nurses brought over at one time, twenty-four died of the fever, and during one month nine members of the medical staff of one of the hospitals succumbed.

One of the first things that the United States Government did in beginning work in the canal zone was to take up the fight against the yellow fever mosquito. In Panama where the water for domestic purposes was kept in cisterns and water-barrels, inspectors were appointed to see that all such receptacles and other possible breeding-places for mosquitoes were kept covered. After the first inspection, 4,000 breeding-places were reported. About six months later there were less than 400. Similar work was done in all the towns and settlements along the route of the canal. In addition to this fight against the yellow fever mosquito considerable attention was paid to the breeding-places of the malarial mosquito. The results have been remarkable. Cases of yellow fever are now rare throughout this zone, and there has been a very great reduction in the extent of the malarial districts. The last case of yellow fever occurred in May, 1906. Before this work was done a man took his life in his hands when he went into this region. Now it is regarded as a perfectly safe place to live. Indeed it is a much safer place than many sections of our own country where proper sanitary measures have not been taken to protect the health of the community.

IN RIO DE JANEIRO

In Rio de Janeiro they have as yet been unable to get rid of the mosquitoes, although thousands of dollars are spent annually in fighting them. But the non-immunes there protect themselves by doing their business in Rio during the day and going back at night to Petropolis, twenty-five miles inland and twenty-five hundred feet higher, where they are safe, for no Stegomyia have ever been found there.

They claim there that the yellow fever mosquito does not bite during the daytime after she has laid her eggs, and that she will not lay her eggs until about three days after she has fed on blood, therefore a Stegomyia that bites during the day will not carry the yellow fever because she is too young. This seems to explain why the fever cannot be contracted by being bitten by a mosquito in the daytime. Certain other experiments, however, have given different results so that as far as we know it is not safe to be bitten at any time by such a mosquito in a region where the disease is endemic or where it is epidemic.

In the main the work of the French Yellow Fever Commission working in Rio de Janeiro has confirmed the findings of the American Commission. One interesting special thing that the French Commission seems to have established is that the female may transmit the infecting power to her offspring, so that it would be possible for a mosquito that had never bitten a yellow fever patient to be capable of infecting a non-immune person. While all this is very probable in the light of what we know of the disease and the way in which other diseases caused by similar organisms may be transmitted by the parent to the offspring, yet the most conservative investigators are waiting for further proof.

HABITS OF STEGOMYIA

The whole fight against yellow fever, then is directed, as we have seen, against the mosquito, Stegomyia calopus. The habits of this species are such as to make it easy in some respects to combat. It is seldom found far away from human habitation. The adults will not fly far. Once in a house they usually stay there except when they leave to deposit their eggs.

On the other hand, some of these same habits make it all the more dangerous. It will breed in almost any kind of water, no matter how filthy, and a very small amount will suffice. Thus any leaks from water-pipes or drains, cisterns, small cans of water or any such places may become dangerous breeding-places. If conditions are unfavorable there will often be developed small individuals which can easily make their way through ordinary mosquito-netting.

Dr. Manson has pointed out an interesting possible result of the crusade that is now being waged against the yellow fever mosquitoes. The immunity of the people native to the endemic regions is supposed to be due to their having had mild attacks of the fever during childhood, for the children in these regions are subject to certain fevers which are probably very mild forms of yellow fever.

Now if we kill practically all of the Stegomyia so that these children do not have this fever there will be developed, in due time, a population most of whom are non-immune.

This freedom from the disease for some time will allow us to grow careless in regard to fighting the mosquitoes. They will be allowed to increase and by some chance the yellow fever will again be introduced and there will then be very grave danger of most extensive and destructive epidemics.

DANGER OF THE DISEASE IN THE PACIFIC ISLANDS

I have already referred once or twice to the conditions in many of the Pacific tropical islands. In some of these various species of Stegomyia are abundant, and in some Stegomyia calopus is the most abundant and troublesome form. All the natives of these islands are non-immune because there has never been any yellow fever there. Unless extraordinary care is taken the disease will be introduced there sooner or later and the results are sure to be most appalling. The climatic and sanitary conditions and the habits of the people are ideal for the development and spread of the disease, and what I have seen of the conditions on some of these islands convinces me that it would be almost impossible to control the disease before it had a chance to kill a large percentage of the population.

With the opening of the Panama Canal these things become more possible. Heretofore, the shipping to these regions has not been from ports where yellow fever was endemic or even likely to be epidemic. But unless the yellow fever is kept out of the canal zone, the danger will be many fold what it is now.

The white man has already carried enough misery to these island peoples in the way of loathsome diseases, and it is to be hoped that this, another great curse, will not be carried to them with our civilization, the beneficial results of which have been so often very justly questioned.

What I have said in regard to these islands applies with equal force and in some instances with even greater force to parts of Asia, the Eastern Archipelago and other places.



CHAPTER IX

FLEAS AND PLAGUE

Plague has always been one of the most dreaded diseases, and when we read of its ravages in the old world and the utter helplessness of the people before it we do not wonder that the very word filled them with horror. One of the greatest scourges ever known began in Egypt about A.D. 542, and spread along the shores of the Mediterranean to Europe and Asia. It lasted for sixty years, appearing again and again in the same place and decimating whole communities.

Another great pandemic, beginning in 1364, spread over the whole of the then known world and appeared in its most virulent form. On account of diffuse subcutaneous hemorrhages it came to be known as the "black death" and of course spread terror in all the communities where it appeared. Whole villages and districts were depopulated. The death-rate was very high, one authority placing the total mortality at twenty-five million.

During this time new centers of infection were established, and since then it has been carried by the commerce of the nations to all parts of the world. It is not restricted, as many other epidemic diseases, to the tropics or semi-tropics, although as a matter of fact we find it is more prevalent in these regions on account of the sanitary conditions.

HOW PLAGUE WAS CONTROLLED IN SAN FRANCISCO

Attention is called to these things in order that we may compare past conditions with present. During the last few years San Francisco has been fighting an outbreak of plague that in other days would have been nothing less than a national calamity. But with modern methods of handling it, based on knowing what it is, what causes it and how it is spread, the authorities there have been able not only to hold the disease in check, but practically to stamp it out with the loss of comparatively few lives.

Dr. Blue of the Public Health and Marine Hospital Service and his co-workers directed their whole energy toward controlling the rats. A small army of men were employed, catching rats in every quarter of the city. Dr. Rucker reports that fully a million rats were slain in this campaign. Their breeding-places were destroyed by making cellars, woodsheds, warehouses, etc., rat-proof and removing all old rubbish. Garbage cans were installed in all parts of the city, as it was required that all garbage be stored where rats could not feed upon it, and altogether every effort was made to make it as uncomfortable as possible for the rats.

The marked success attending this work abundantly confirms the soundness of the theory upon which it was based, and serves as another example of the way in which science is teaching us how to prevent or control many of our most serious diseases.

THE INDIAN PLAGUE COMMISSION

In 1896, what proved to be a very serious outbreak of plague, occurred in Bombay and spread to other parts of India. In 1898, a commission was appointed to inquire into the origin of the different outbreaks, the manner in which the disease is communicated, etc. This was known as the Indian Plague Commission, and its exhaustive report, together with the minutes of the evidence presented to the committee, represents a stupendous amount of work on this subject and is the basis for much of the later investigation that has been undertaken.

After the consideration of the evidence from various sources the commission decided that the principal mode of infection both for man and rats was through some sort of an abrasion in the skin, although it recognized also the possibility of infection through the nose and throat, and possibly, very rarely, through the intestinal tract or other places.

Considerable time was spent in considering Dr. Simond's claim, made in 1898, that fleas which have been parasitic on plague-infected rats migrate on the death of their hosts and convey the infection to healthy men and rats. Dr. Simond sought to establish the following:

"Firstly, that plague rats are eminently infective when infected with fleas and that they cease to be infective when they have been deserted by their parasites: Secondly, that living plague bacilli are found in association with fleas which are taken from plague-infected rats: Thirdly, that plague can pass from infected rats to other animals which have not come directly in contact with them or with their infected excretions: Fourthly, that fleas which infest rats will transfer themselves as parasites to men."

After reviewing the experiments which had been made to establish these claims the commission believed that sufficient precaution had not been taken to prevent infection from other sources and that not enough definite evidence was produced. Against this claim much negative evidence was considered and the final conclusion was "that suctorial insects do not come under consideration in connection with the spread of plague."

In 1905 another body of men known as the Advisory Committee was appointed to arrange for further studies in India and other places, particularly in relation to the mode of dissemination of the disease. They at once appointed a new working commission who immediately began their studies and experiments. The preliminary reports of their work, which are still known as the Reports of the Indian Plague Commission, as well as the reports of contributing investigations that are being made from time to time, have served to establish entirely Dr. Simond's claims and have completely revolutionized the methods of fighting plague.

There are several different types of plague, seeming to depend largely on the manner of infection. The most common type is that known as the bubonic plague which is characterized by buboes or swellings in various parts of the body. This form of infection is usually received through the skin in some manner or other. Only rarely does direct man-to-man infection occur though there is always the possibility of it. The investigations have shown that the flea is the most common agent in transferring the disease from rat to rat or from rat to man. This may be accomplished by the flea transferring the bacilli directly from one host to another on its proboscis, or they may be carried in the alimentary canal of the flea and gain an entrance into the skin through an abrasion of some kind when the flea is crushed as it is biting, or when some of the bacilli are left on the skin in the excreta of the insect.

RESULTS OF VERJBITSKI'S EXPERIMENTS

A very important series of experiments bearing directly on this subject was made in 1902 and 1903 by Dr. D.T. Verjbitski. The paper giving the results of this work was not published in any scientific journal until 1908 when the Advisory Committee published it in one of their reports. The experiments were so well planned and executed and the results so definite that I think it is worth while to give in full his summary of results. The bugs referred to are bedbugs.

"(1) All fleas and bugs which have sucked the blood of animals dying from plague contain plague microbes.

"(2) Fleas and bugs which have sucked the blood of animals which are suffering from plague only contain plague microbes when the bites have been inflicted from 12 to 26 hours before the death of the animals, that is, during that period of their illness when their blood contains plague bacilli.

"(3) The vitality and virulence of the plague microbes are preserved in these insects.

"(4) Plague bacilli may be found in fleas from four to six days after they have sucked the blood of an animal dying with plague. In bugs, not previously starved or starved only for a short time (one to seven days), the plague microbes disappear on the third day; in those that have been starved for four to four and one-half months, after eight or nine days.

"(5) The numbers of plague microbes in the infected fleas and bugs increase during the first few days.

"(6) The faeces of infected fleas and bugs contain virulent plague microbes as long as they persist in the alimentary canal of these insects.

"(7) Animals could not be infected by the bites of fleas and bugs which had been infected by animals whose own infection had been occasioned by a culture of small virulence, notwithstanding the fact that the insects may be found to contain abundant plague microbes.

"(8) Fleas and bugs that have fed upon animals which have been infected by cultures of high virulence convey infection by means of bites, and the more certainly so the more virulent the culture with which the first animal was inoculated.

"(9) The local inflammatory reaction in animals which have died from plague occasioned by the bites of infected insects is either very slight or absent. In the latter case it is only by the situation of the primary bubo that one can approximately identify the area through which the plague infection entered the organism.

"(10) Infected fleas communicate the disease to healthy animals for three days after infection. Infected bugs have the power of doing so for five days.

"(11) It was not found possible for more than two animals to be infected by the bites of the same bugs.

"(12) The crushing of infected bugs in situ during the process of biting, occasioned in the majority of cases the infection of the healthy animal with plague.

"(13) The injury to the skin occasioned by the bite of bugs or fleas offers a channel through which the plague microbes can easily enter the body and occasion death from plague.

"(14) Crushed infected bugs and fleas and their faeces, like other plague material, can infect through the small punctures of the skin caused by the bites of bugs and fleas, but only for a short time after the infliction of these bites.

"(15) In the case of linen and other fabrics soiled by crushing infected fleas and bugs on them, or by the faeces of these insects the plague microbes can under favorable conditions remain alive and virulent during more than five months.

"(16) Chemical disinfectants do not in the ordinary course of application kill plague microbes in infected fleas and bugs.

"(17) The rat flea Typhlopsylla musculi does not bite human beings.

"(18) Human fleas do bite rats.

"(19) Fleas found on dogs and cats bite both human beings and rats.

"(20) Human fleas and fleas found on cats and dogs can live on rats as casual parasites, and therefore can under certain conditions play a part in the transmission of plague from rats to human beings, and vice versa."

RESULTS OF VARIOUS INVESTIGATIONS

Various other plague commissions from other countries as well as many individuals have investigated the same subject, and the results all point conclusively to the fact that the rats and the fleas are at least the most important factors in the spread of the disease. The evidence from many sources and from many experiments may be briefly summed up as follows: The disease is caused by the presence in the system of minute bacteria, Bacillus pestis. It is probable that plague is primarily a disease of rats and only secondarily and accidentally, as it were, a disease of man.

Rats are subject to the plague and are often killed by it in great numbers. An outbreak of plague among men is often preceded by a very noticeable outbreak among rats.

Rats dying of the plague have their blood filled with the plague bacillus. Fleas or other suctorial insects feeding on such rats take myriads of these bacilli into their stomach and get many on their proboscis.

The fleas usually leave a rat as soon as it dies and of course seek some other source of food. When such infected fleas are permitted to bite other rats or guinea-pigs these animals often develop the disease. Several of the species of fleas that infest rats will bite man also, and in the cases of many plague patients it can be definitely shown that they had recently been bitten by fleas.

STRUCTURE AND HABITS OF FLEAS

A study of the structure and habits of fleas shows that in many respects they are particularly adapted for spreading such a disease as bubonic plague. The piercing proboscis consists of three long needle-like organs, the epipharynx and mandibles, and a lower lip or labium. The mandibles have the sides serrate like a two-edged saw. The labium is divided close to its base so that it really consists of two slender four-segmented organs which lie close together and form a groove in which the piercing organs lie. When the flea is feeding, the epipharynx and mandibles are thrust into the skin of the victim, the labium serving as a guide. As the sharp cutting organs are thrust deeper and deeper the labium doubles back like a bow and does not enter the skin. Saliva is then poured into the wound through minute grooves in the mandibles, and the blood is sucked up into the mouth by the sucking organ which lies in the head at the base of the mouth-parts. Just above this piercing proboscis is a pair of flat, obtuse, somewhat triangular pieces, the maxillary blades or maxillae. When the proboscis is fully inserted into the skin the tips of these maxillae may also be embedded in the tissue and perhaps help to make the wound larger. Attached to these maxillae is a pair of rather stout, four-jointed appendages, the palpi. They probably act as feelers.

If the flea chances to be feeding on a plague-infected rat or person many of the plague bacilli will get on the mouth-parts and myriads of them are of course sucked up into the stomach with the blood. Those on the proboscis may be transferred directly to the next victim that it is thrust into, and those in the stomach may be carried for some time and finally liberated when the flea is feeding again or when it is crushed by the annoyed host. The latter is probably the most common method of infection, for the bacilli that are liberated when the flea is crushed may readily be rubbed into the wound made by the flea bite or into abrasions of the skin due to the scratching. Kill the flea, but don't "rub it in."



During the recent outbreak in San Francisco many thousand fleas that were infesting man, rats, mice, cats, and dogs, squirrels and other animals have been studied and it has been found that while each flea species has its particular host upon which it is principally found, few if any of them will hesitate to leave this host when it is dead and attack man or any other animal that may be convenient.

COMMON SPECIES OF FLEAS

Throughout India and in all the warm climates where plague frequently occurs the most common flea found on rats has come to be known as the plague flea (Laemopsylla cheopus) (Figs. 105, 106), and is doubtless the principal species that is concerned in carrying the disease in those climates. It now occurs quite commonly on the rats in the San Francisco Bay region and is occasionally found there on man also. In the United States, Great Britain and other temperate regions another larger species, Ceratophyllus fasciatus is by far the most common flea found on rats, and is commonly known as the rat flea. It occurs on both the brown and the black rats Mus norvegicus and M. rattus, on the house mouse and frequently on man. It has also been taken in California on pocket gophers and on a skunk.

The common human flea (Pulex irritans) (Figs. 108, 109), is found in all parts of the inhabited world. Although we regard it primarily as a pest of human beings it often occurs very abundantly on cats, dogs, mice and rats as well as on some wild mammals such as badgers, foxes and others and has occasionally been found on birds.

Most entomologists regard the fleas commonly found on cats and dogs as belonging to one species Ctenocephalus canis. Others believe them to be distinct species and call the cat flea Ctenocephalus felis. So far as our personal comfort and safety is concerned it makes but little difference to us whether the flea that bites us is called canis or felis for they both look very much alike, and act alike and the bite of one hurts just as much as the bite of the other. Although cats and dogs are their normal hosts they are very often troublesome household pests, sometimes making a house almost uninhabitable. They are frequently found on rats, and therefore may carry the plague bacillus from rat to rat or from rat to man.

GROUND-SQUIRRELS AND PLAGUE

As early as 1903 Dr. Blue, in charge of the plague suppressive measures in San Francisco, became impressed with the possibility of the common California ground-squirrels (Otospermophilus beecheyi), acting as an agent in the transmission of plague. It was rumored at that time that some epidemic disease was killing the squirrels in some of the counties surrounding San Francisco Bay, notably in Contra Costa County. None of the squirrels were examined at that time, but since then many thousand have been carefully studied and it has been definitely shown that many of them are plague-infected. Just how the plague got started among them will probably never be really known. There is little doubt, however, but that it was transferred in some way from the rats to the squirrels. The trains and the bay and river steamers running out from San Francisco would afford abundant opportunity for the rats to go from the city to the warehouses all along the shore. Once there they would use the same runways as the squirrels about the warehouses and in the near-by fields. In harvest time the rats migrate to the fields and make constant use of the squirrel holes. The farmers in some sections report that they frequently catch more rats than squirrels in traps set in squirrel holes at that season of the year.

This close association of the rats and the squirrels affords a good opportunity for the fleas infesting them to pass from one host to the other.

So far only two species of fleas have been recorded from the ground-squirrels. One, Ceratophyllus acutus, is very common, sometimes literally swarming over the squirrels, particularly if a squirrel is sick or weak from any cause. The other species, Hoplopsyllus anomalus, is less abundant but still quite common. Both of these species infest rats also, so the chain of evidence is practically complete. We have only to assume that at sometime one or more of the plague-infected rats found their way into the region where the squirrels were, and the fleas passing from the rats to the squirrels would carry the plague with them.

The fact that the plague already has such a start among the squirrels opens a new and very serious phase of the problem of suppressing the disease. All who have hunted the ground-squirrels will testify to the readiness with which the fleas from them will bite those who are handling them. As it is the sick or weak squirrels that are most often taken there is always a chance that plague may be transferred from them to human beings. The records of the plague cases in California show at least three cases in which there seems to be very little doubt that the disease resulted from handling plague-infected squirrels.



A still more serious thing is the possibility of the disease remaining in a more or less virulent form among the squirrels for some time, possibly for years, and then breaking out again in some locality where the rats or men may become infected. As long as there is a trace of the disease among the squirrels there is always the chance of it spreading, so that new areas may become infested. Those in charge of the plague-suppressive measures are fully aware of these dangers and are making a careful study of the situation and will doubtless be able to cope with it successfully. It may be that the squirrels will have to be exterminated in the infected regions. This would be a long and difficult task, but the success attending the fight against the rats in a great city shows what can be done when the determination to do it is there.

REMEDIES FOR FLEAS

We have seen how a great city set to work to rid itself of the plague-sick rats. As a matter of fact it was not the rats that they were after primarily. If the rats had not harbored fleas the city would have been glad to let the disease take its course and destroy as many rats as possible. But it was found that the only way to get rid of the fleas that might possibly be infected with the plague was to kill their rat hosts.

General cleaning-up measures will of course very materially lessen the number of fleas about the private dwellings, but there often remains a number of fleas in the house that are a source of great annoyance even if the danger is eliminated.

Particularly is this apt to be so in places where cats or dogs are members of the household. These animals almost always harbor at least a few fleas, and where there are a few there is always a possibility, even a great probability, that there will be many more unless an effort is made to get rid of them.

In some sections of the country it is the cat and dog flea that is the most troublesome to man. The minute white eggs of the fleas are usually laid about the sleeping-places of these animals and the slender active larvae that hatch from them feed upon any kind of organic matter that they can find in the dust or in the cracks and crevices. About eight or ten days after hatching the larvae spin delicate brownish cocoons in which they pass the pupal stage, issuing a few days later as the adult fleas.

It will at once appear, then, that it is important to provide the cats and dogs with sleeping-places that can be kept clean. If they have a mat or blanket to sleep on this can be taken up and shaken frequently and the dust swept up and burned. In this way many of the eggs or larvae may be destroyed. Very often the dust under a carpet that has not been taken up and dusted for some time will be found to be harboring a multitude of fleas or their larvae. In such cases a thorough cleaning of the carpet and the floors will bring relief. Houses that are unused for some time during the summer months are often found to be overrun with fleas in the fall, for the fleas have had an unmolested opportunity to breed and multiply. Such rooms of course require a thorough cleaning or it is sometimes possible to kill the fleas by a liberal use of pyrethrum powder or benzine or to fumigate. In this connection, Dr. Skinner's note in the Journal of Economic Entomology is worth repeating.

"In the latter part of last May (1908) I moved into a house that had not been previously occupied. No carpet was used and being summer only a few rugs were placed on the floors. A part of the household consisted of a collie dog and three Persian cats. Very soon the fleas appeared, the dog and cat flea, Ctenocephalus canis. I did not count them and I can't say whether they numbered a million or only a hundred thousand. On arising in the morning and stepping on the floor one would find from three to a dozen on the ankles. The usual remedies for fleas are either drastic or somewhat unsatisfactory. The drastic one is to send the animals to the institutions, where they are asphyxiated, or take the other advice, 'Don't keep animals.'

"I tried mopping the floors with rather a strong solution of creolin but it did little good. Previous experience with pyrethrum was not very satisfactory. Knowing the volatility of naphthalene in warm weather and the irritating character of its vapor led me to try it. I took one room at a time, scattered on the floor five pounds of flake naphthalene and closed it for twenty-four hours. On entering such a room the naphthalene vapor will instantly bring tears to the eyes and cause coughing and irritation of the air passages. I mention this to show how it acts on the fleas. It proved to be a perfect and effectual remedy and very inexpensive, as the naphthalene could be swept up and transferred to other rooms. So far as I am concerned the flea question is solved and if I have further trouble I know the remedy. I intend to keep the dog and the cats."



CHAPTER X

OTHER DISEASES, MOSTLY TROPICAL, KNOWN OR THOUGHT TO BE TRANSMITTED BY INSECTS

SLEEPING SICKNESS

One of the worst scourges of Africa and one that is to-day attracting world-wide attention is the disease known as trypanosomiasis, the terminal phase of which is sleeping sickness, one of the most ghastly diseases that we know.

Among the Protozoa referred to in one of the earlier chapters mention was made of certain trypanosomes which inhabit the blood of man and certain animals. Very little was known concerning these parasites previous to the beginning of the present century, but since that time several have been found to be of great economic importance. The group is being studied extensively and every day our knowledge of them is increasing so that we now know quite definitely the life-history of several.

Trypanosoma lewisi, a parasite of rats, is perhaps the best known as it is always common where-ever rats are found. Sometimes as many as 30% or 40% of the rats of certain districts are infected. It is thought that these are transmitted from rat to rat by the common rat-louse which serves as an intermediate host. Fleas may also act as disseminating agents.

A few other kinds cause serious disease of animals, but we are more interested just now in the particular one that is causing so much trouble in Africa. This parasite was discovered in 1902 and was named Trypanosoma gambiensi (Fig. 111). Since then it has been found to be widely distributed. Although the natives have doubtless long been subject to the disease caused by this parasite, the recent influx of whites to these regions and the consequent movements of the natives have caused a great spread of the disease so that whole regions are now made desolate, the inhabitants dying or fleeing to escape the uncanny death.

The disease may run its course in a few months or it may take years. The symptoms are various, but infection is usually soon followed by fevers, sometimes mild, sometimes severe, which recur at irregular intervals. Certain glands or other parts of the body may become swollen. More or less extensive skin eruptions occur on all parts of the body and the patient gradually becomes anemic and physically and intellectually feeble. The nervous system seems to be affected by the parasite, either directly or by the action of the toxins it produces. The patient becomes more debilitated and morose with an increasing tendency to sleep, hence the name sleeping sickness. As the stupor deepens the patient looses all desire or power of exertion and as little food is taken he rapidly wastes away and finally succumbs for after this final stage is reached there is no relief.

It is definitely known that a species of tsetse-fly, Glossina palpalis (Fig. 112), which somewhat resembles our stable-fly, is responsible for the dissemination of the disease, and some recent investigators have suggested that certain species of mosquitoes may also carry the parasite from one host to another. There still remains some doubt as to the exact manner in which the fly transmits the disease, but it seems altogether likely that it is an alternative host and does not serve as a simple mechanical carrier. In this respect it is like the mosquito which is one of the necessary hosts of the malaria parasites, and unlike the house-fly which carries the germs of various diseases in a purely mechanical way without serving as a definite necessary host for the parasite.

The tsetse-fly is found only in tropical Africa and is limited in its distribution there to certain very definite, narrow, brushy areas along the water's edge. If these places can be avoided there seems to be little danger. Those who are fighting the disease have found that if the brush in the vicinity of watering-places and ferry-landings is cleared away such places become comparatively safe. These flies do not lay eggs but produce full-grown larvae which soon pupate in the ground.

ELEPHANTIASIS

In many tropical regions human blood as well as that of other animals is the normal habitat of certain worm-like parasites (Nematodes). They are not entirely confined to the tropics but may extend far up into the subtropical regions. Five or six different species of these parasites are known, only one of which, however, has been shown to be of any pathological importance, as far as human beings are concerned.



This species, Filaria bancrofti, is not only very widely distributed, but in regions such as some of the South Sea Islands a very large per cent of the natives have the filariae present in their blood. When these parasites are withdrawn from the circulation and placed on a slide for study they are seen to be minute transparent, colorless, snake-like organisms inclosed in a very delicate sack or sheath. They are but a little more than one-hundredth of an inch long and about as big around as a red blood-corpuscle. These are the larval forms of the parasite and have been called by Le Dantec the micro-filaria.

If blood of the patient drawn from the skin, is examined during the day few if any of these parasites are found, but if it is examined between five or six o'clock in the evening and eight or nine o'clock the next morning they may be found in numbers. During the daytime they have retired from the peripheral circulation to the larger arteries and to the lungs, where they may be found in great numbers.

This night-swarming to the peripheral circulation has been found to be a remarkable adaptation in the life-history of the parasite, for it has been demonstrated that in order to go on with its development these larval forms must be taken into the alimentary canal of the mosquito. Most of the mosquitoes in which the development takes place are night-feeders, so that the parasites are sucked up with the blood of the victim. Once inside the stomach they soon free themselves from the inclosing sheath and make their way through the walls of the stomach and enter the muscular tissue, particularly the thoracic muscles. Here they undergo a metamorphosis and increase enormously in size, some attaining one-sixteenth of an inch in length.

After sixteen to twenty days they leave these muscles and make their way to other parts of the body. A few may be found in different parts of the abdomen, but most of them make their way forward into the head of the mosquito and coil themselves up close to the base of the proboscis, finally finding their way down into the proboscis inside the labium. Here they lie until an opportunity offers for them to escape to the warm blood of a vertebrate. They probably pass through the thin membrane connecting the labella with the proboscis and there find their way into the wound made by the puncture when the insect bites. Whether these parasites can gain an entrance into the circulatory system in any other way is not known. It has been suggested that the mosquitoes dying and disintegrating on the surface of water may liberate the filariae which may later find their way into the system of the vertebrate host when the water is used for drinking, but most of the investigations made so far seem to indicate that they make their way directly from the proboscis into the new host.

Soon after entering the circulatory system of the human host the parasites make their way into the lymphatics where they attain sexual maturity, and in due time new generations of the larval filariae or microfilariae are poured into the lymph, and finally into the definite blood-vessels, ready to be sucked up by the next mosquito that feeds on the patient.

In most cases of infection the presence of these filariae in the blood seems to cause no inconvenience to the host. They are probably never injurious in the larval stage, that is, in the stage in which they are found in the peripheral circulation.

In many cases, however, the presence of the sexual forms in the lymphatics may cause serious complications. The most common of these is that hideous and loathsome disease known as elephantiasis in which certain parts of the patient becomes greatly swollen and distorted. An arm or a leg may become swollen to several times its natural size, or other parts of the body may be seriously affected.

In some of the South Sea Islands 30% to 40% of the natives are afflicted in this way, some only slightly others seriously. There is little or no pain, but in severe cases the distorted parts often render the patient entirely helpless.

The exact way in which the parasites cause such swelling is not very definitely known. Manson, who has done more work on these diseases than any one else, believes that the trouble arises from the clogging of the lymphatic glands or trunks, thus cutting them off from the general circulation, in which case the affected parts may become distorted. This clogging of the passages is believed to be due to the presence of great numbers of immature eggs which have been liberated by parasites injured in some way before their eggs were entirely developed.

This interference with the lymphatic circulation brings about the anomalous condition of a patient with a serious filarial disease with fewer of the filarial parasites in his blood than one who is not so seriously affected. This is supposed to be due to the fact that the disease-producing parasites have died and that the lymphatics have become so obstructed that any microfilariae they may contain cannot make their way into the general circulation. Such a patient then would not be as likely to infect a mosquito as would one less seriously affected.

It has always been thought that little or nothing could be done in the way of successfully treating this disease, but quite recently a French physician, who has been conducting a long series of experiments in the Society Islands, announced that he is able to cure many cases by certain surgical operations on the affected parts.

DENGUE OR "BREAKBONE FEVER"

This is another disease of the tropics often occurring in widespread epidemics. It is probably most frequently met with in the West Indies, but may occur in any of the tropical countries or islands. Occasionally it spreads into subtropical or even temperate regions. Several extensive epidemics have occurred in the United States. Once introduced into a community it spreads very rapidly and nothing seems to confer immunity.

The various names by which it has been called well describe its effect on the patient; breakbone fever, dandy-fever, stiff-necked or giraffe-fever, boquet (or "bucket") fever, scarlatina rheumatica, polka-fever, etc. While the suffering is intense as long as the disease lasts it seldom terminates fatally.

It has always been classed as a very contagious disease and it has not yet been definitely shown that it is not. Recent observations, however, have shown that it is probably caused by a certain Protozoan parasite that is found in the blood of dengue patients and several experiments have been conducted by Dr. Graham which seem to indicate that it is transmitted by mosquitoes. In these experiments, Culex fatigans, a common tropical or subtropical mosquito, was used. The same parasite that is found in the human blood may be found in the stomach and blood of the mosquitoes up to the fifth day after it has fed on a dengue patient.

Sick and healthy individuals were allowed to remain in close contact in a room from which the mosquitoes had been excluded, and the disease was not spread. Mosquitoes that had bitten dengue patients were taken to a higher region where dengue had never occurred and allowed to bite two healthy persons. Both developed the disease and as they were protected from other mosquitoes until they had recovered, the disease did not spread to others of the community. These and other observations seem to make a complete chain of evidence, and most medical men to-day accept the theory as well proved and in their practice take every precaution to prevent the spread of the disease by keeping the infected patient from being bitten by the mosquitoes.

The yellow fever mosquito is also suspected of carrying this same disease, and it is possible that other species are also concerned. If it is true that the parasite can be carried by several different species of mosquitoes this would account very largely for its rapid spread wherever it is introduced into a community. Where it occurs outside the tropics it is only in the warm summer months when mosquitoes are always abundant.

MALTA OR MEDITERRANEAN FEVER

This is also a tropical and subtropical disease that occasionally gets up into the temperate region, sometimes occurring in the United States. The fever begins with a severe headache, and other symptoms follow. It is usually of the remittent type and may continue for some months.

It is caused by minute bacteria (Micrococcus melitensis) and is a very infectious but not usually contagious disease. The germ is readily conveyed by inoculation, and several investigators have sought to show that the mosquito often serves as the inoculating agent. The disease is especially prevalent during the mosquito season, and has twice been conveyed to monkeys by infected insects.

LEPROSY

This loathsome disease has long been known to be caused by a particular bacillus (Bacillus leprae), but the way in which this organism gains an entrance into the system is still unknown. Many theories have been propounded, but none of them has been well established. Within recent years the possibility of insects carrying the germ and in one way or another transmitting it to healthy individuals has been suggested and much discussed. As the leprae bacilli are present in the skin and ulcers of leprous patients, insects sucking the blood or feeding on the sores could not help taking some of them into their body or becoming contaminated. These bacilli have been found at various times in the stomach or intestine of mosquitoes, fleas and bedbugs. So it is believed by some that these and other insects, such as lice and flies, may sometimes transmit the disease. On a previous page we have referred to the possibility of the face-mites acting as disseminators of leprosy.

Leprosy occurs most commonly among people where little attention is paid to bodily cleanliness. Such people are usually freely infested with various parasites that thrive well in the filth, so if the germs can be transmitted in this way the carriers are there in abundance.

The fact that the sores usually occur on exposed parts of the body has been pointed to as evidence that inoculation is due to such insects as flies and mosquitoes. It has been noted that leprosy is frequently very common in regions where elephantiasis occurs, suggesting the possibility of the same carrier, the mosquito, for both diseases. So while there is as yet very little evidence one way or the other, insects that are found around leprous patients are to be regarded with suspicion, for until we know more definitely just how the disease is communicated the insects must be looked on as possible sources of contamination.

KALA-AZAR OR DUM-DUM FEVER

This is a very fatal infectious disease of many tropical and subtropical regions, spreading terror among the natives wherever it occurs. It is caused by the presence in the system of Protozoan parasites, the so-called Leishman-Donovan bodies, that have recently been studied by several observers.

Dr. W.S. Patton of the Indian Medical Service has been making some extensive experiments with the common bedbug of India (Cimex rotundatus) which seem to demonstrate fully that this insect is responsible for the transmission of the parasite that causes the disease. He has found the parasite in all stages of development in the bedbug. This, taken with a number of other observations in regard to the tendency of the disease to cling to particular houses, makes a strong case against the bedbug. Manson, however, believes that the parasite may be transmitted by other agents also, possibly by means of flies that visit the sores or in other ways.

ORIENTAL SORE

This disease, once supposed to be confined to the Orient, is now found to be rather widely distributed throughout the tropics, where it is sometimes very prevalent. It is caused by the presence in the system of a parasite very similar to or identical with the one causing kala-azar and is regarded by some as a modified form of that disease. The patient is affected with one or more serious sores or ulcers which usually occur on exposed parts of the body.

The parasite that causes the disease is supposed to be carried by insects either directly or indirectly.

In the latter case the insect may act as an intermediate host.

Dogs and camels are also attacked by this disease and may be sources of infection.



BIBLIOGRAPHY

A complete list of books and articles dealing more or less directly with the subjects discussed in this book would be too extended for use here. For the past ten or twelve years many of the medical and biological journals have contained articles in almost every issue, discussing these subjects in some of their phases. I have selected only a few of the more important of them, and these only the English ones, confining myself mostly to those that I have personally consulted, and giving brief annotations. Many of these will be found to include very full bibliographies of the particular subject treated.

In order to avoid repetition, references are given under one head only although many might properly be included in other sections as well.

PARASITES AND PARASITISM

BRAUN, MAX. Animal Parasites of Man. Translated by Pauline Falcke and edited by L.W. Sambon and F.V. Theobald. Third edition, 1906. A chapter on the general subject of parasitism and a description of parasites of all classes. Bibliography.

LEUCKART, R. The Parasites of Man and the Diseases Induced by Them. Eng. transl., London, 1886.

NEUMAN, THEO. Entoparasites and Hygiene. Trans. Vassar Bros. Institute, VII, 1895. A general discussion of parasitism; life-history of some common parasites that infest man.

NEUMANN, L.G. Treatise on the Parasites and Parasitic Diseases of the Domesticated Animals. Eng. transl. by Fleming, 1892.

RANSOM, B.H. How Parasites Are Transmitted. Year Book U.S. Dept. Agric., 1905, pp. 139-166 (pub. 1906). Discusses the ways in which parasites of all classes are transmitted.

SAMBON, L. The Part Played by Metazoan Parasites in Tropical Pathology. Jour. Trop. Med. & Hyg., Vol. XI, Jan. 15, 1908. A comprehensive discussion of this subject.

SHIPLEY, A.E., AND FEARNSIDES, E.G. Effects of Metazoan Parasites on Their Hosts. Jour. Econom. Biology, Vol. I, 1906, pp. 41-62. Discusses injury due to mere presence of parasite in host; to the migration of the parasite; loss to host by feeding of parasites; injury by certain toxins.

STILES, C.W. Diseases Caused by Animal Parasites. Osler's Mod. Med., Vol. I, 1907, p. 525. General discussion; Trematodes; Cestodes; Roundworms; Acariasis; Parasitic Insects; Myiasis.

VAN BENEDEN, P.J. Animal Parasites and Messmates. 1889. Contains much that is interesting.

WARD, HENRY B. Influence of Parasitism on the Host. Proc. Amer. Assn. for Advancement of Science, Vol. 56, 1907. A comprehensive statement of this subject. List of literature.

PROTOZOA

CALKINS, G.N. The Protozoa. Osler's Mod. Med., Vol. I, 1907, p. 353. General notes on the Protozoa; classification; reproduction; life-cycle of various forms. Regards Protozoa as subkingdom and the four great divisions as phyla.

CALKINS, G.N. Protozooelogy. N.Y., 1909. Chapters on parasitism, pathogenic Protozoa, etc.

CLARKE, J.J. Protozoa and Disease. London, 1903, Pt. I. Discusses the various protozoa that cause disease, and refers frequently to those that are transferred from host to host by insects.

CLARKE, J.J. Protozoa and Disease. London, 1908. Part II, comprising sections on the causation of smallpox, syphilis and cancer. Notes on parasitic Protozoa, tropical diseases, ticks, piroplasmosis, etc.

DANIELS, C.W. Persistence of the Tropical Diseases of Man Due to Protozoa. Jour. Trop. Med. & Hyg., 12, Aug. 2, 1909, pp. 232-234. Same in Lancet, II, 1909, p. 460. Good summary of present knowledge of the subject.

MINCHIN, E.A. Protozoa. In Albutt and Rolleston's System of Medicine, II, 1907, pp. 9-122. A comprehensive chapter on Protozoa. Many parasitic forms are figured and described. Bibliography.

MINCHIN, E.A. The Sporozoa. In Lankester's Treatise on Zooel., Pt. I, pp. 150-360, 1903. Best account of this group, list of Sporozoan hosts. Bibliography.

BACTERIA

FLEXNER, SIMON. Relation of Bacteria and Sporozoa to Disease. Science, N.S., Vol. 27, No. 682, pp. 133-136. On these pages discusses relation of bacteria and Protozoa to human diseases.

JORDAN, EDWIN O. General Bacteriology. Philad., 1898. A good general treatment of the subject.

LEVY, ERNST, AND KLEMPERER, FELIX. Elements of Clinical Bacteriology for Physicians and Students (transl. by A.A. Eschner), Philad., 1909. Morphology and biology of bacteria; infection; immunity; specific diseases of bacterial origin, etc.

MUIR, ROBT., AND RITCHIE, JAS. Manual of Bacteriology. N.Y., 1903. Contains chapter on the relation of bacteria to diseases and discussion of several bacterial diseases.

STERNBERG, G.M. A Manual of Bacteriology. N.Y., 1893. Part III is devoted to pathogenic bacteria.

INSECTS AND DISEASE

HERMS, W.B. Medical Entomology, Its Scope and Methods. Jour. of Eco. Ento., Vol. 2, No. 4, 1909, pp. 265-268.

HOWARD, L.O. Insects as Carriers and Spreaders of Disease. Year Book U.S. Dept. Agric., 1901, pp. 177-192. Good review of the subject.

HOWARD, L.O. How Insects Affect Health in Rural Districts. U.S. Dept. Agric., Farmers' Bulletin, No. 155, 1902. Discussion of city and county conditions; protection from typhoid, malaria and yellow fever.

HOWARD, L.O. Economic Loss to the People of U.S. Through Insects That Cause Disease. Bull. 78, U.S. Dept. Agric. Bur. of Ent., 1909. A comprehensive discussion and summary of the subject. Discusses mosquitoes, flies, the Panama Canal, epidemic diseases and the progress of nations.

KELLOGG, V.L. Insects and Disease, Chap. XVIII, in American Insects, pp. 615-654, 1905. Discusses Mosquitoes and malaria; yellow fever and filariasis.

KING, H.H. Report on Economic Entomology of Khartoum, in Third Rept. of Wellcome Research Lab., 1908. Discusses insects injurious to man: mosquitoes, blood-sucking insects other than mosquitoes, etc.

MASON, C.F. The Spread of Diseases by Insects, with Suggestions Regarding Prophylaxis. International Clinics, Vol. II, 1904, pp. 1-21. A brief summary of the subject.

MCCRAE, JOHN. Recent Progress in Tropical Medicine. International Clinics, Vol. II, 1904, pp. 22-36. Discusses several diseases, some of which are transmitted by insects.

NUTTALL, G.H.F. On the Role of the Insects Arachnids and Myriapods as Carriers in the Spread of Bacterial and Parasitic Diseases of Man and Animals. A critical and historical study. Johns Hopkins Hospital Reports, Vol. 8, 1899, pp. 1-154. A review of all the literature up to this date. Important article.

NUTTALL, G.H.F. Insects as Carriers of Disease. Recent advances in our knowledge of the part played by blood-sucking arthropods (exclusive of mosquitoes and ticks) in the transmission of infectious diseases. Bericht ueber den XIV. Intern. Kongress fuer Hygiene und Dermogrophic. Berlin, 1907, pp. 195-206. Discusses protozoan and bacterial diseases.

STILES, C.W. Insects as Disseminators of Disease. Virginia Medical Semi-monthly, Vol. 6, No. 3, May 10, 1901, pp. 53-58. Good statement of subject with list of recent workers.

WHERRY, W.B. Insects and Infection. Cal. State Jour. of Med., Nov., 1907. Discusses the role of insects, ticks, etc., in the transmission of infectious diseases.

Symposium on Yellow Fever and Other Insect-borne Diseases. Science, N.S., Vol. 23, Nos. 584-585, 1906. The Protozoan Life-cycle, G.N. Calkins. Filariasis and Trypanosome Diseases, H.B. Ward. The Practical Results of Reed's Findings on Yellow Fever Transmission, J.H. White. Difficulties of Recognition and Prevention of Yellow Fever, Q. Kohnke. The Practical Side of Mosquito Extermination, H.C. Weeks. Without Mosquitoes There Can Be No Yellow Fever, Jas. Carroll. Estivo-autumnal Fever, Cause, Diagnosis, Treatment and Destruction of Mosquitoes Which Spread the Disease, H.A. Veazie.

MOSQUITOES—SYSTEMATIC AND GENERAL

BALFOUR, ANDREW, AND STAFF. Second Report of the Wellcome Research Laboratories at the Gordon Memorial College, Khartoum, 1906. Includes reports on work on mosquitoes and other noxious insects.

BOYCE, SIR ROBERT W. Mosquitoes or Man? The Conquest of the Tropical World. N.Y., 1909. Reviews medical and sanitary work in the tropics and discusses the relation of insects to various tropical diseases.

BUSCH, AUGUST. Report on a Trip for the Purpose of Studying the Mosquito Fauna of Panama. Smith. Miscell. Coll., Vol. 5, Pt. I, 1908, p. 49. Work that is being done in Panama to control the mosquitoes. Annotated list of species.

FELT, E.P. Mosquitoes or Culicidae of New York State. In N.Y. State Museum Bull. 79, Entomology 22, 1904. Discusses distribution, migration and life-history of various species of mosquitoes and mosquito diseases. Bibliography.

GILES, GEO. M. A Handbook of Gnats or Mosquitoes, Giving the Anatomy and Life-History of the Culicidae. London, 1902. Whole subject treated very fully.

GRUBBS, S.B. Vessels as Carriers of Mosquitoes. Pub. Health and Mar. Hospt. Ser. Bull. II, Mar. 3, 1903. Believes that mosquitoes may come aboard when the vessel is lying at anchor one-half mile from shore, and that under favorable conditions they may come aboard when the vessel is fifteen miles from shore.

HOWARD, L.O. Mosquitoes. Osler's Mod. Med., Vol. I, p. 370, 1907. General notes on classification and habits particularly in relation to diseases.

HOWARD, L.O. Notes on Mosquitoes of the United States. U.S. Dept. Agric., 1900. Div. of Ento. Bull. No. 25, N.S. Account of the structure; biology; remarks on remedies.

HOWARD, L.O. Concerning the Geographic Distribution of the Yellow Fever Mosquito. Public Health Rept., Pub. Health and Mar. Hospt. Ser., Nov. 13, 1903. The same revised to Sept. 10, 1905.

HOWARD, L.O. Mosquitoes: How They Live; How They Carry Disease; How They Are Classified; How They May Be Destroyed. N.Y., 1901. One of the best popular books on mosquitoes.

MCCRACKEN, I. Anopheles in California, with a Description of a New Species. Entomological News, Vol. 15, Jan., 1904. Records of three species, their breeding-places, habits, etc.

MITCHELL, EVELYN G. Mosquito Life. N.Y., 1907. A good popular account of the mosquitoes and their relation to disease. The appendix treats of mosquitoes and their possible relation to leprosy.

SMITH, J.B. Mosquitoes Occurring Within the State of New Jersey. Report of the New Jersey State Agric. Exper. Station upon the mosquitoes occurring within the State. Trenton, N.J., 1904. Habits, development, relation to disease, checks and remedies; systematic.

SMITH, J.B. The General Economic Importance of Mosquitoes. Popular Science Monthly, 70, 1907, pp. 325-329. Mosquitoes affect not only the health and comfort of the people, but hinder development of agriculture and thus affect land values.

SMITH, J.B. The New Jersey Salt-marsh and Its Improvement. New Jersey Agricultural Experiment Station Bulletin, 207, 1907. Shows that the increased value of the land drained in the antimosquito crusade more than pays for the cost of the drainage.

THEOBALD, F.V. Monograph of Culicidae of the World. Four Vols. and one Vol. of plates. London, 1901 to 1907. Vol. I contains 96 pages on structure, life-history, habits, etc. Vol. II contains a bibliography. Vol. Ill contains a list of species that carry disease.

THEOBALD, F.V. Mosquitoes or Culicidae. In Albutt and Rolleston's System of Medicine, II, 1907, pp. 122-168. Structure, life-history, habits, distribution and classification of mosquitoes. Bibliography.

MOSQUITO ANATOMY

BERKELEY, WM. M. Laboratory Work with Mosquitoes. N.Y., 1902. Chapters on development, anatomy, dissection, malarial parasites, filarial disease, yellow fever.

DIMMOCK, GEO. Anatomy of the Mouth-parts and Suctorial Apparatus of Culex. Psyche, 3, pp. 231-241, Sept., 1881. Good.

IMMS, A.D. On the Larval and Pupal Stages of Anopheles maculipennis. Journal Hygiene, Vol. 7, No. 2, April, 1907. Morphology.

IMMS, A.D. On the Larval and Pupal Stages of Anopheles maculipennis. Parasitology, Vol. I, No. 2, June, 1908. Continuation of article in Jour. Hyg., Vol. 7, No. 2. Continues discussion of morphology.

NUTTALL, GEO. F., CORBETT, LOUIS, AND STRANGEWAYS-PIG, T. Studies in Relation to Malaria. Pt. I, The Geographical Distribution of Anopheles in Relation to the Former Distribution of Ague in England. Jour. Hyg., Vol. I, No. 1, Jan., 1901.

NUTTALL, GEO. F., AND SHIPLEY, ARTHUR E. Studies in Relation to Malaria. Pt. II, Structure and Biology of Anopheles, Jour Hyg., Vol. I, No. 1, Jan., 1901: The Egg and Larva; Bibliography. Pt. II, cont, Vol. I, No. 2, April, 1901: The Pupa. Pt. II, cont., Vol. I, No. 4, Oct., 1901: Adult External Anatomy. Pt. II, cont., Vol. 2, No. 1, Jan., 1902: AEtiology of Adult. Pt. II, cont., Vol. Ill, No. 2, April, 1903: Anatomy of Adult.

THOMPSON, MILLETT T. Alimentary Canal of the Mosquito. Proc. Bost. Soc. Nat. Hist., Vol. 32, No. 6, 1905, pp. 145-202. Good summary of recent investigations.

WESCHE, W. The Mouth-parts of Nemocera and Their Relation to the Other Families of Diptera. Royal Microscopic Soc. Jour., 1904, pp. 28-47. Discussion with illustrations of the mouth-parts of various Diptera.

MOSQUITOES—LIFE-HISTORY AND HABITS

AYERS, E.A. The Secrets of the Mosquito. A guide to the extermination of the prolific pest. World's Work, 1907, Vol. 14, pp. 8902-8910. Notes on life-history and methods of control.

JORDAN, E.O., AND HEFFERAN, MARY. Observations on the Bionomics of Anopheles. Jour. Infec. Diseases, II, 1905, pp. 56-69. Occurrence, breeding-places, habits, etc.

MORGAN, H.A., AND DUPREE, J.W. Development and Hibernation of Mosquitoes. Bull. 40, N.S., Div. of Ento., pp. 88-92, 1903. Results of observation on five genera of mosquitoes in the vicinity of Baton Rouge, La.

ROSS, E.H. The Influence of Certain Biological Factors on the Question of the Migration of Mosquitoes. Jour. Trop. Med. & Hyg., 12, 1909, pp. 256-258, Sept. 1. Only fecundated females feed on blood, and must be fertilized after each batch of eggs. This determines largely the time and place of breeding.

SMITH, J.B. Concerning Migration of Mosquitoes. Science, 18, Dec. 11, 1903, pp. 761-764. Observations on the migrations of mosquitoes, particularly C. sollicitans.

MOSQUITO FIGHTING

CELLI, ANGELO. The Campaign Against Malaria in Italy. Transl. by J.J. Eyre. Jour. Trop. Med. & Hyg., XI, Apr. 1, 1908, pp. 101-108. Includes a good discussion of the effectiveness of destroying the mosquitoes in controlling malaria.

FELT, E.P. Mosquito Control. In Report of the N.Y. State Entomologist for 1905, pp. 109-116. Notes on importance and methods of control of various species.

GOLDBERGER, JOS. Prevention and Destruction of Mosquitoes. Public Health Reports, Pub. Health and Mar. Hospt. Ser., July 17, 1908. Life-histories and methods of fighting larvae, pupae and adults.

LE PRINCE, J.A. Mosquito Destruction in the Tropics. Jour. Amer. Med. Assn., LI, p. 26, Dec. 26, 1908. Occurrence and habits of Anopheles, methods of destruction. Results of anti-malarial work on the isthmus. Discussion by various doctors.

QUAYLE, H.J. Mosquito Control Work in California. Bull. No. 178, Calif. Agric. Ex. Sta., pp. 1-55, 1906. Habits and life-history of California species, with an account of experiments to control the salt-marsh species.

ROSENAN, M.J. Disinfection Against Mosquitoes with Formaldehyde and Sulphur Dioxid. Hyg. Lab. Pub. Health and Mar. Hospt. Ser., Bull. 6, 1901.

ROSS, RONALD. Mosquito Brigades and How to Organize Them. New York, 1902.

ROSS, RONALD. Logical Basis of the Sanitary Policy of Mosquito Reduction. Science, N.S., Vol. 22, No. 750, Dec. 1, 1905, pp. 689-699. Important article dealing with the methods of control.

SMITH, J.B. Salt-marsh Mosquitoes. New Jersey Agric. Exper. Stn. Special Bulletin T, 1902. Breeding-places and methods of control of this species.

SMITH, J.B. Mosquitocides. Bull. 40, New Series U.S. Dept. Agric., Div. of Ento., pp. 96-108, 1903. Results of experiments with a number of substances, several of which were found to be effective and some cheap enough to permit of their use to a limited extent.

SMITH, J.B. The New Jersey Salt-marsh and Its Improvement. Bull. No. 207, Nov. 14, 1907, New Jersey Agric. Exper. Stn. Results of draining the marshes to get rid of mosquitoes.

SMITH, J.B. The House Mosquito: a City, Town and Village Problem. N.J. Agric. Ex. Stn. Bull. 216, 1908. Work done on salt-marshes since 1904 practically eliminated the migratory species, so that C. pipens, the house mosquito, is now the problem. Life-history and methods of combating.

UNDERWOOD, W.L. Mosquitoes and Suggestions for Their Extermination. Pop. Sci. Mo., Vol. 63, 1903, pp. 453-466. Life-history, habits and methods of control.

UNDERWOOD, W.L. The Mosquito Nuisance and How to Deal with It. Boston, 1903.

First Antimosquito Convention, 1903. Pub., Brooklyn, 1904. Contains articles on what railroads, government and laws should do toward mosquito extermination; mosquito work in Havana; how state appropriations should be used, etc.

National Mosquito Extermination Society. Bulletin No. 1, 1904. Object of Society; brief sketches of Ross, Reed, and others. Reprints of a few articles on mosquito extermination.

American Mosquito Extermination Society. Year Book for 1904-05. N.Y., 1906. Containing reports of meetings and discussions of various problems. Several interesting papers, among them "Criminal Indictment of the Mosquito," F.W. Moss. "Mosquito Work at Panama Canal," W.C. Sorgas. "Diversities Among New York Mosquitoes," E.P. Felt. "Mosquito Extermination in New Jersey," J.B. Smith. "The Mosquito Question," Quitman Kohnke.

Antimalarial Work in the Panama Canal Zone. Editorial in Jour. Trop. Med. & Hyg., XI, Aug. 15, 1908, p. 251. Notes on the success of the measures adopted there.

MOSQUITOES AND DISEASE

DOTY, A.H. The Mosquito, Its Relation to Disease and Its Extermination. New York State Journal of Medicine, May, 1908.

FINLAY, CHAS. Mosquitoes Considered as Transmitters of Yellow Fever and Malaria. Med. Record, May 27, 1899, pp. 737-739. Review of his theory in regard to mosquitoes and disease and the probable necessary changes in view of recent discoveries.

HOWARD, L.O. Mosquitoes as Transmitters of Disease. Review of Reviews, XXIV, 1901, pp. 192-195. A review of the work of various investigators.

SMITH, J.B. Sanitary Aspect of the Mosquito Question. Medical News, Mar. 7, 1903. Note on mosquitoes and their relation to disease.

TAYLOR, J.B. Observations on the Mosquitoes of Havana, Cuba. Reprint from La Revista de Medicina, June, 1903, p. 27.

MALARIA

BANKS, C.S. Experiments in Malarial Transmission by Means of Myzomyia ludlowii. Phil. Jour. Sci., B. 2, 1907, pp. 513-535. Breeding-places of mosquitoes, life-histories of the species; mosquitoes and malaria.

CRAIG, C.F. Malarial Fevers. Osler's Mod. Med., Vol. I, p. 392, 1907. Historical; distribution; malarial parasites; classification; development; malarial mosquitoes; pathology; treatment, etc.

CRAIG, C.F. Studies in the Morphology of Malarial Plasmodia after the Administration of Quinine and in Intracorpuscular Conjugation. Jour. Infec. Diseases, VII, No. 2, 1910. See also same, IV, 1907, pp. 108-140. Gives the evidence upon which he bases his theory of the meaning of intracorpuscular conjunction.

CRAIG, C.F. The Malarial Fevers, Hemoglobinuric Fever and the Blood Protozoa of Man. N.Y., 1909. A thorough consideration of the subject of malaria and good discussion of the other subjects noted in title. Bibliography.

DEADERICK, W.H. Malaria. Philad., 1909. The chapter on aetiology treats of the transmission by mosquitoes.

HARRIS, S. Prevention of Malaria. Jour. Amer. Med. Assn., 53, Oct. 9, 1909, pp. 1162-67. Effects of malaria, transmission by mosquitoes, etc. In the discussion of the paper J.H. White summarizes the fight against yellow fever in New Orleans.

HERRICK, G.W. Relation of Malaria to Agriculture and Other Industries of the South. Economic losses occasioned by malaria; malaria responsible for more sickness among the white population than any other disease; relation to mosquitoes. Pop. Sci. Mo., Vol. 62, Apr., 1903, pp. 521-525.

JONES, ROSS, ELLETT. Malaria. London, 1907. Small book, introduction by Ross. Malaria in Greece and Italy; shows how this disease contributed to the downfall of great nations.

MANNABERG, JULIUS. Malaria. In Nothnagel's Encyclopedia of Practical Med., Amer. Ed., 1905, pp. 17-494. A very comprehensive discussion of the disease and the relation of mosquitoes to the malarial parasite.

MANSON, PATRICK. The Mosquito and the Malaria Parasite. Brit. Med. Jour., Vol. II for 1898, pp. 849-853. History of the parasite in the human and insect host; observations of Ross and others and their meaning.

MANSON, PATRICK. Experimental Demonstration of the Mosquito-malarial Theory. Brit. Med. Jour., Vol. 2 for 1900, pp. 949-951, also Lancet, II, 1900, pp. 923-925. Infected mosquitoes sent from Rome allowed to bite men in England who had not been in malarial regions. Malarial fever followed.

MANSON, PATRICK. Malarial Fever. Appendix to Vol. IX of T.C. Albutt's System of Med., 1900. Relation of the malarial parasite to the disease and to mosquitoes.

ROBERTSON, E.W. Renaming of Malaria—Anophelesis. Va. Medical Semi-monthly, Sept. 10, 1909. Considers malaria a misnomer and gives reasons for suggesting new name.

ROSS, RONALD. On Some Peculiar Pigmented Cells Found in Two Mosquitoes Fed on Malarial Blood. Brit. Med. Jour., 1897, Dec. 18, p. 1786. Records in his experiments in feeding mosquitoes on blood of malarial patients. Records finding the parasites in some of them. Important article.

ROSS, RONALD. Pigmented Cells in Mosquitoes. Brit. Med. Jour., 1898, Feb. 26, p. 550. Further notes on them.

ROSS, RONALD. The Mosquito Theory of Malaria. Report dated Calcutta, Feb. 16, 1899. Reprinted in Pop. Sci. Monthly, Vol. 56, Nov., 1899, pp. 42-46. Tells of his investigations in India and their results.

ROSS, RONALD. The Relationship of Malaria and the Mosquito. Lancet, II, 1900, July 7, p. 4880. Observation on the transmission of malaria.

ROSS, RONALD. Malaria Fever, Its Cause, Prevention and Treatment. London, 1902. Chapters on malaria, mosquitoes, prevention and treatment.

ROSS, RONALD. Parasites of Mosquitoes. Jour. of Hyg., VI, No. 2, Apr., 1906. Brief review of several of his earlier papers on this subject with additional notes.

SIMPSON, W.J.R. Recent Discoveries Which Have Rendered Antimalarial Sanitation More Precise and Less Costly. Brit. Med. Jour., 1907, II, pp. 1044-46. Discussion of the various factors in mosquito control.

STEPHENS, J.W.W., AND CHRISTOPHERS, S.R. The Practical Study of Malaria and Other Blood Parasites. London, 1908. Chapters on mosquitoes, flies and ticks and their relation to diseases.

STERNBERG, G.M. The Malarial Parasite and Other Pathogenic Protozoa. Pop. Sci. Mo., Vol. 50, 1897, pp. 628-641. Account of the discovery of the malarial parasite and more recent studies on it.

STERNBERG, G.M. Malaria. Smith. Rept., 1900, pp. 645-656. Review of the experimental evidence in support of the mosquito-malaria theory.

Malarial Fever. Jour. Trop. Med. & Hyg., II, Mar. 16, 1908, pp. 96-98. A list of literature mostly for the years 1906 and 1907.

YELLOW FEVER

ADAMS, S.H. Yellow Fever, a Problem Solved. The battle of New Orleans against the mosquito. McClure's Magazine, Vol. 27, June, 1906, p. 178. An interesting popular article.

CARROLL, JAMES. Yellow Fever. Osler's Mod. Med., Vol. II, 1907, p. 736. History, aetiology, treatment. A good review of the work of the Yellow Fever Com. and the results of their work.

CARROLL, JAMES. The Transmission of Yellow Fever. Amer. Med. Assn., 40, 1905, pp. 1429-33. Shows the relation of the mosquito to the disease.

CARROLL, JAMES. Yellow Fever. Lessons to be learned from the present outbreak of yellow fever. Jour. of Amer. Med. Assn., Vol. 45, 1905, pp. 1079-81. Among other things recommends that mosquitoes be kept from patients.

CHAILLE, S.E. The Stegomyia and Fomites. Amer. Med. Assn., 40, 1903, pp. 1433-40. Concludes that the mosquito is the only proven disseminator of yellow fever. Extended discussion by various physicians.

DASTRE, A. The Fight Against Yellow Fever. Smith. Rept., 1905, pp. 339-350. History of the yellow fever epidemics, its geographical distribution, and the work that is being done to control it.

DOTY, A.H. On the Mode of Transmission of the Infectious Agent in Yellow Fever and Its Bearing upon the Quarantine Regulations. Med. Record, Oct. 26, 1901, pp. 649-653. Review of older theories in regard to the spread of yellow fever. Believes that the quarantines are now unnecessary.

FINLEY, CHAS. The Mosquito Theory of the Transmission of Yellow Fever and Its New Development. Med. Record, Jan. 19, 1901. Refers to his early observations on the subject, giving extracts from some of his earlier papers to show that he had long held the mosquito responsible for the dissemination of yellow fever.

GOLDBERGER, JOS. Yellow Fever, AEtiology, Symptoms and Diagnosis. Yellow Fever Inst. Bull. 16, Pub. Health and Mar. Hospt. Ser., 1907. Includes discussion of the relation of mosquitoes to the disease.

GUITERAS, JOHN. Experimental Yellow Fever at the Inoculation Station of the Sanitary Department of Havana. Amer. Med., Vol. II, No. 21, 1901, pp. 809-817. Experiments show that all types of the yellow fever from mild to severe may be produced by the bite of the mosquito.

MCFARLAND, JOSEPH. Life and Work of James Carroll. Memoir read at the fifth annual meeting of the Soc. of Tropical Med., 1908. Early life of Carroll and his work with the Yellow Fever Com.

PARKER, H.B., BEYER, G.E., AND POTHIER, O.L. Rept. of Working Party No. 1, Yellow Fever Institute. Bull. 13, Pub. Health and Mar. Hospt. Ser., 1903. As a result of their studies they believe that the disease is caused by a protozoan parasite which they name and describe. Discuss the relation of mosquitoes to the disease.

REED, WALTER; CARROLL, JAMES; AND AGRAMONTE, A. Experimental Yellow Fever. Amer. Med., July 6, 1901, pp. 15-23. Records of certain experiments and their results.

REED, WALTER; CARROLL, JAMES; AND AGRAMONTE, C.A. The AEtiology of Yellow Fever. A preliminary note presented at the Amer. Pub. Health Assn. Philad. Med. Jour., Oct. 27, 1900, pp. 790-796. Also an additional note in Jour. Amer. Med. Assn., 36, pp. 431-440, 1901. Records of their experiments and a summing up of the data in regard to yellow fever and the mosquito.

REED, WALTER, AND CARROLL, JAMES. The Prevention of Yellow Fever. Med. Record, Oct. 26, 1901, pp. 441-449. History of the disease, especially in U.S., results of the work of Yellow Fever Com. description, life-history and habits of the mosquito, its relation to yellow fever, methods of control. Important paper.

REED, WALTER. Recent Researches Concerning the AEtiology, Propagation and Prevention of Yellow Fever by U.S. Army Com. Jour. Hyg., 2, 1902, pp. 101-119. Review of work of the Yellow Fever Com. and the importance of the results. Bibliography.

ROSENAN, M.J., PARKER, H.B., FRANCIS, E., AND BEYER, G.E. Rept. of Working Party No. 2, Yellow Fever Institute. Experimental studies in yellow fever and malaria at Vera Cruz, Mex. U.S. Pub. Health and Mar. Hospt. Ser., May, 1904. Includes experiments and observations on mosquitoes.

ROSENAN, M.J., AND GOLDBERGER, JOS. Report of Working Party No. 3, Yellow Fever Institute. Yellow Fever Inst. Bull. 15, Pub. Health and Mar. Hospt. Ser., 1906. Unsuccessful attempts to grow the yellow fever parasite. Negative results in the experimental study of the hereditary transmission of the yellow fever in the mosquito. Appendix A gives a translation of Marchoux and Simonds' report in which they report positive results in their experiments along the same line.

STERNBERG, G.M. Transmission of Yellow Fever by Mosquitoes. Smith. Rept., 1900, pp. 657-673. Review of the early theories in regard to yellow fever and the work and findings of the yellow fever commission.

WHITE, J.H. Yellow Fever and the Mosquito. Jour. Amer. Med. Assn., LI, No. 26, Dec. 26, 1908. Considers both S. calopus and C. pungens. Results of early mistakes. Necessity of destroying mosquito. Methods of destroying mosquito. Habits of mosquito.

Abstract of the Report of the French Yellow Fever Com. at Rio de Janeiro, 1903. Pub. Health Report, Pub. Health and Mar. Hospt. Ser., Vol. 19, Pt. I, p. 1019. A summary of their findings and conclusions to the date of report.

DE YBARRA, A.M.F. Yellow Fever Again in Cuba. Jour. Trop. Med. & Hyg., XI, Mar. 2, 1908, pp. 73-78. Cites a number of cases of yellow fever within the last few years and uses them as evidence to show that the disease may be transmitted in other ways than by the mosquito. A strong summing up of the arguments against the mosquito theory. Reprint of editorial in Tex. Med. Jour., Oct., 1907, also follows this article.

The Extinction of Yellow Fever at Rio de Janeiro. Lancet, II, 1909, p. 404. A review of a French publication giving the results of the work from 1903 to present time. In 1903 before work was begun there were 584 deaths from yellow fever. In 1908 only 4, and none so far in 1909. Success accredited to mosquito work and general sanitation.

A Pioneer in Research on Yellow Fever. Editorial in Brit. Med. Jour., May 30, 1908, p. 1306. Refers to the work of L.D. Beauperthuy, who, in 1853, set forth the theory that yellow fever was transmitted by mosquitoes.

DENGUE

ASHBURN, P.M., AND CRAIG, C.F. Experimental Investigations Regarding the AEtiology of Dengue Fever. Jour. Infec. Diseases, Vol. V, 1907, pp. 440-475. Conclude that the disease is spread only by mosquitoes.

COLEMAN, THOMAS D. Dengue. Osler's Mod. Med., Vol. II, 1907, p. 489. AEtiology, pathology, etc.; possibility of Culex fatigans disseminating the disease.

GRAHAM, H. "The Dengue"; a Study of Its Pathology and Mode of Propagation. Jour. of Trop. Med. & Hyg., July 1, 1903, p. 209. Experiments which seem to show that dengue is transmitted by Culex fatigans.

LEICHTENSTERN, O. Dengue. In Nothnagel's Encyclopedia of Practical Med., Amer. Ed., 1905, pp. 720-743. Consideration of the disease and its transmission.

ROSS, E.H. The Prevention of Dengue Fever. Amer. Trop. Med. & Parasit., Vol. II, No. 3, July 1, 1908, pp. 193-195. A successful campaign against the mosquitoes in Port Said in 1906 stopped the outbreaks of malaria and dengue.

Dengue and Sand-flies. Jour. Trop. Med. & Hyg., 12, 1909, pp. 172-173. A note on these pages refers to the work of Dr. R. Doerr, who suspects that dengue may be carried by sand-flies, Phlobotomus, as well as by mosquitoes.

FILARIAL DISEASES AND ELEPHANTIASIS

CHRISTOPHERS, S.R. What Is Really Known of the Cause of Elephantiasis. Ind. Med. Gaz., Nov., 1907, p. 404. Questions Manson's theory in regard to the disease being caused by filaria.

MANSON, PATRICK. Tropical Diseases. London, 1908, pp. 594-648. A most comprehensive chapter on filariasis and elephantiasis.

PHALEN, J.M., AND NICHOLS, H.J. Filariasis and Elephantiasis in Southern Luzon. Phil. Jour. Sci., Sept., 1908. Culex microannulatus regarded as the carrier of the filaria.

PROUT, W.T. On the Role of Filaria in the Production of Disease. Jour. Trop. Med. & Hyg., Apr. 1, 1908, p. 109. Discussion of same in same journal, June 1, 1908.

WHITE, DUNCAN. Filarial Periodicity and Its Association with Eosinophilia. Jour. Trop. Med. & Hyg., 12, July 15, 1909, pp. 175-183. Among other things he discusses the relation of mosquitoes to filarial diseases.

LEPROSY

BRINCKERHOFF, W.R. A Note upon the Possibility of the Mosquito Acting in the Transmission of Leprosy. Pub. Health and Mar. Hospt. Ser. (general publications), 1908. Suggests the possibilities of such transmission, but concludes that the probabilities are against it.

GOODHUE, E.S. The Bacillus Leprae in the Gnat and Bedbug. Ind. Med. Gaz., Vol. XLI, Aug., 1906, p. 342. Has found this bacillus in mosquitoes and bedbugs, but believes the latter is more concerned in transmitting the disease.

GOODHUE, E.S. Mosquitoes and Their Relation to Leprosy in Hawaii. Amer. Med., N.S., 2, 1907, p. 593. Suggests that mosquitoes may carry the disease, also warns against danger from flies and bedbugs.

HUTCHINSON, J. Mosquitoes and Leprosy. Brit. Med. Jour., Dec. 22, 1906, Vol. II, p. 1841. Evidence against the insect theory of transmission of leprosy.

MUGLISTON, T.C. On a Possible Mode of Communication of Leprosy. Jour. Trop. Med., Vol. VIII, July 15, 1905, p. 209. Suggests that the itch-mite may be the carrier of leprosy. Studies on 77 lepers led him to this conclusion.

SMYTH, W.R. Leprosy. Brit. Med. Jour., Dec. 8, 1906, Vol. II, p. 1670. Believes that bedbugs or some similar wingless parasite conveys the disease.

PLAGUE

BRANNERMAN, W.B. Spread of Plague in India. Jour. of Hyg., Vol. 6, No. 2, Apr., 1906, pp. 179-211. A digest of experiments made in India. Discusses various ways in which the disease may be spread. Review of the evidence that insects may be concerned. Bibliography.

CALVERT, W.J. Plague. Osler's Mod. Med., Vol. II, 1907, p. 760. History; bacteriology; pathology; plague among animals; transmission, etc.

HAM, B. BURNETT. Report on Plague in Queensland, 1900-1907. P. 153 discusses the rat-flea theory of dissemination of bubonic plague, summing up the evidence of various observers, including the Indian Advisory Com. and others. Considers the evidence conclusive that P. cheopis and possibly C. fasciatus transmit plague. Other pages discuss various rat fleas and their relation to plague in rats.

HANKIN, E.H. On the Epidemiology of Plague. Jour. Hyg., 5, 1905, pp. 48-83. A comprehensive discussion of the disease and its spread, several pages devoted to rats and fleas; evidence for and against the theory that rats and fleas are the principal carriers of the disease.

HERZOG, MAX. The Plague, Bacteriology, Morbid Anatomy & Histopathology, Including the Consideration of Insects as Plague Carriers. Biological Laboratory Bureau of Govt. Laboratories, Manila, Oct., 1904. Reviews the evidence regarding the possibility of fleas carrying plague; describes a new rat flea (Pulex philippinensis); records experiments with fleas and cites a case of bubonic plague in a child in which the infection was possibly carried by Pediculi.

MCCOY, G.W. Plague Bacilli in Ectoparasites of Squirrels. Pub. Health Reports, Pub. Health and Mar. Hospt. Ser., Vol. XXIV, No. 16, Apr. 16, 1909. Experiments with fleas and lice from infected squirrels demonstrating presence of plague bacilli.

MCCOY, G.W. The Susceptibility of Gophers, Field-mice and Ground-squirrels to Plague Infection. Jour. of Infec. Diseases, Vol. 6, 1909, No. 3, pp. 283-288. Gophers highly resistant, field-mice moderately susceptible and ground-squirrels very susceptible to plague.

MITZMAIN, M.B. Insect Transmission of Bubonic Plague: a Study of the San Francisco Epidemic. Ento. News, 19, No. 8, 1908, pp. 353-359. Fleas obtained in examination of 1,800 rats. Attempt to locate source of rat and flea introduction.

MORTON, F.M. Eradicating Plague from San Francisco. Report of the Citizens' Health Com. and an account of its work. San Francisco, 1909. Discusses the epidemics, methods of transmission, methods of fighting, etc.

RUCKER, W.C. Plague Among Ground-squirrels in Contra Costa Co., Cal. Pub. Health Reports, Pub. Health and Mar. Hospt. Ser., Aug. 27, 1909. Reports of human cases supposed to be connected with plague among ground-squirrels. Plague among squirrels; habits, methods of fighting, etc.

RUCKER, W.C. Fighting an Unseen Foe. Sunset Mag., XXII, No. 2, Feb., 1909. Story of the fight against plague in San Francisco.

SHIPLEY, A.E. Rats and Their Animal Parasites. Jour. Eco. Biology, Vol. III, No. 3, Oct. 28, 1908. List of species of ecto- and endoparasites.

SIMPSON, W.J. A Treatise on Plague. Cambridge Univ. Press, London, 1906. Deals with historical, epidemiological, clinical, therapeutic and preventive aspect of the disease.

THOMPSON, J.A. The Mode of Spread and Prevention of Plague in Australia. Lancet, Oct. 19, 1907, p. 1104. Rat fleas the essential factor in transmitting plague, and preventive methods should be directed against the rats.

THOMPSON, J.A. On the Epidemiology of Plague. Jour. Hyg., Vol. VI, No. 5, Oct., 1906. Methods of infection, spread, relation of rats to the disease and a review of the rat-flea theory. Bibliography.

VERJBITSKI, D.T. The Part Played by Insects in the Epidemiology of Plague. Jour. Hyg., 8, 1908, No. 2, pp. 162-208. Record of extensive experiments with fleas. Fleas communicated plague for three days, bedbugs for five days. Interrelation of fleas, rats, dogs, cats, and man. An important article translated from Russian.

WHERRY, W.B. Further Notes on the Rat Leprosy and on the Fate of the Human and Rat Leper Bacillus in Flies. Jour. Infec. Diseases, Vol. 5, No. 5, 1908. Discussion and references, experiments with flies, summary, etc. More than 1,115 lepra-like bacilli were counted in a single fly-speck.

WHERRY, W.B. Plague Among the Ground-squirrels of California. Jour. Infec. Diseases, Vol. 5, No. 5, 1908, pp. 485-533. How the plague was first discovered among rats, records of cases and a discussion of the possible relation of this to human plague cases.

Eradicating Plague in San Francisco; Report of the Citizens' Health Committee, 1909. An account of the recent outbreaks and the methods of fighting them.

Report of the Indian Plague Commission, Vol. V, pp. 75-77, 1901. In these pages the Commission considers the question of the transference of plague by suctorial insects. It considers Simonds' claims and others and believes that "suctorial insects do not come under consideration with the spread of plague."

Reports on Plague Investigations in India Issued by the Advisory Committee Appointed by the Sec. of State for India, the Royal Society and the Lister Institute. The reports include the reports of the Working Commission appointed by the Advisory Committee and reports on various contributory investigations. They are published in the Jour. of Hygiene as "Extra Plague Numbers." All these reports deal very largely with the relation of the rat and flea to plague, and are commonly referred to as "Reports of Indian Plague Commission." The first number, Vol. VI, Sept., 1906, contains articles on "Experiments upon the Transmission of Plague by Fleas." "Note on the Species of Fleas Found on Rats, Mus rattus and Mus decumanus in Different Parts of the World." "The Physiological Anatomy of the Mouth-parts and Alimentary Canal of the Indian Rat Flea, Pulex cheopis," and other papers on the relation of rats to plague. The second number, Vol. VII, July, 1907, contains articles on "On the Significance of the Locality of the Primary Bubo in Animals Infected with Plague in Nature," "Further Observations on the Transmission of Plague by Fleas with Special Reference to the Fate of Plague Bacillus in the Body of the Rat Flea," "Experimental Production of Plague Epidemics Among Animals," "Experiments in Plague Houses in Bombay," "On the External Anatomy of the Indian Rat Flea and Its Differentiation from Some Other Common Fleas," "A Note on Man as a Host of the Indian Rat Flea," and others on the relation of rats to plague. The third number, Vol. VII, Dec., 1907, contains articles on "Digest of Recent Observations on the Epidemiology of Plague" (Bibliography), "Epidemiological Observations in Bombay City," "Epidemiological Observations in the Villages of Wadhala, Parel, Worli in the Neighborhood of Bombay Village," "General Considerations Regarding the Spread of Infection, Infectivity of Houses, etc., in Bombay City and Island," "Epidemiological Observations in the villages of Dhand and Kasel (Punjab)." The fourth number, Vol. VIII, May, 1908, contains articles on "The Part Played by Insects in the Epidemiology of Plague" (see also ref. under D.T. Verjbitski), "Observations on the Bionomics of Fleas with Special Reference to P. cheopis," "The Mechanism by Means of Which the Flea Cleans Itself of Plague Bacilli," "On the Seasonal Prevalence of Plague in India."