The lesions were focal and appeared to be of the type found in the brain in Chagas' disease. The parasites were intracellular and were seen in the cytoplasm of a variety of cells, associated or unassociated with the lesions. The occurrence of the parasites in other organs was by no means a constant finding although they were noted in the lungs, kidneys, spleen, heart, and liver. A surprising pathologic finding, of which no mention has been made in the literature, was the extensive invasion of the nerves by this parasite, with the production of inflammatory lesions. Since the parasite is infective and pathogenic for a number of hosts, it has been isolated and maintained in guinea pigs. Intraperitoneal inoculations of infective material causes death of the animals in from 6 to 10 days with widespread invasion of lungs. and central nervous system. A peculiar type of peritonitis is occasioned with the production of a considerable amount of a mucinous fluid in which are suspended round cells, macrophages and mesothelial cells, many containing large numbers of parasites.

Although Toxoplasma sp., has been known to occur in a wide variety of animals for some 40 years, it has never been considered of any importance as a pathogen. However, in the past few years it has been proven to be the cause of a fatal encephalomyelitis in human beings, particularly in infants and young children, and in several instances it has been associated with a fatal type of pneumonia. It is quite possible, because of difficulties in diagnosis, that the role of this parasite as an important pathogenic agent has been overlooked.

During the year some 600 stool examinations were made. The following table shows what parasites were found and their relative. incidence.

These percentages are based on one examination only and would be higher if more than one stool specimen could have been examined. The figures, however, give some idea of the infection rate, for each of the parasites, in a cross section group of Panama City and suburbs.

Fifty-four surgical specimens were prepared and examined. Among these four malignancies were encountered: A basal-cell carcinoma, a metastatic carcinoma of the stomach, an adamantinoma, and a large cell lymphosarcoma of the posterior dorsum of the tongue.

Our interest in, and work on, equine and bovine trypanosomiasis has continued. Because of the present world conditions the principal drug used in the treatment of equine trypanosomiasis is no longer available and the necessity of finding a substitute led to the testing, under field conditions, of one which has shown some promise in experimental infections in laboratory animals. This drug, the sodium salt of P-carbamylamino-phenylarsonic acid, was tried on the horses naturally infected with Trypanosoma hippicum and on two experimentally infected. Two apparent cures were obtained in the naturally infected group. When the opportunity is presented for more carefully controlled treatment, it is planned to continue this work.

A colony of vampire bats has been maintained at the laboratory ever since it was found that they are vectors of Trypanosoma hippicum. They have been kept in order to study longevity and breeding possibilities in captivity. One bat has now been with us for over 9 years and two others have each lived in captivity for 8 years. Three of the females have each produced a single offspring that lived to maturity and is now an adult member of the colony. Our records now show that one bat infected with the horse trypanosome (T. hippicum) survived the disease and has shown no relapse or carrier state. This is the only instance of survival. All other bats infected with the disease died within a month.

The department has made every effort to aid and cooperate in the work being carried on by Col. H. S. Eakins, Chief of the United States Military Mission to Panama. Sterile solutions, culture media, fixing and preserving solutions and other supplies have been provided for post mortem examination of animals and the tissues collected have been prepared and examined microscopically. On numerous occasions it has been possible to assist in blood surveys.

Activities of Senior Sanitary Engineer W. H. W. Komp, United States Public Health Service.-Mr. Komp continues as chairman of the subcommittee on entomology of the Pan American Sanitary Conference and has extended his study of disease-bearing mosquitoes in many parts of Central and South America. In July 1942 he was appointed consultant in malariology to the Division of Health and Sanitation of the Office of the Coordinator of Inter-American Affairs. In that capacity he has visited the units of that organization in Haiti, Panama, Colombia, Ecuador, Peru, Brazil, and Paraguay, assisting them in their antimarlaria operations. During the year he also visited the Galapagos Islands to make a resurvey of mosquito conditions for the United States Army. He continues to receive for identification large mosquito collections from various units of the Rockefeller Foundation located in South America and he is doing similar work for the units of the division of health and sanitation of the Institute of Inter-American Affairs in Central and South America. Since the publication of his extensive paper on The Anopheline Mosquitoes of the Caribbean Region (Bull. 179, National Institute of Health, Washington, D. C.), he has published a short paper on a new Anopheles mosquito of wide distribution, probably a carrier of malaria, found in Brazil, Argentina, and Bolivia.

Chief of the United States Military Mission to Panama.-Col. H. S. Eakins, Veterinary Corps, United States Army, arrived August 20, 1942, to take up his duties in the Republic of Panama. In order to facilitate his work, and to make the cooperation of the Gorgas Memorial Laboratory easier to maintain, he was given office space at the laboratory and provided with technical assistance on animal surveys. His activities have been concerned with the epidemiology of domestic animal diseases, the control of such diseases, and the giving of advice in veterinary practice. The chief subjects for his special investigations during the year have been trypanosomiasis of equine stock (T. hippicum) and trypanosomiasis of cattle (T. vivax). Experiments in the treatment of these diseases with arsenicals and the antimony compounds have been conducted in many regions of the republic. A total of 48 blood-film surveys were made, 21 on horses, and 27 on

cattle. These included 1,354 horses and 707 head of cattle. Of the 2,061 thick-blood films examined by the Gorgas Memorial Laboratory, 63 from horses revealed the parasites of T. hippicum and 47 from cattle showed T. vivar. Coincident findings also record piroplasmosis in 49 horses and 8 cattle and filariasis in 8 horses and 2 cattle. Pathological examinations were made also on necropsy materials secured from a mule in the province of Chiriqui and from a cow in the province of Darien. Dermal myiasis of cattle due to Dermatobia hominis Linn. has also been receiving attention. This affects cattle so extensively in some parts of Panama that it is of considerable importance from a purely economic standpoint. Preventive measures by the use of repellents and by the use of various killing fluids that can be applied to the warbles in the skin with a brush were instituted. Colonel Eakins has stimulated the formation of quarantine laws and encouraged a study for the improvement of the breeds of stock and the betterment of forage. The arrangement with the Republic of Panama for his services has been renewed for another year.

Cooperation with military and other Government agencies.-Opportunities to cooperate with units of the United States armed forces stationed in the Isthmian area have increasingly engaged the attention of the members of the laboratory staff. Every effort has been made to meet the demand for assistance to military personnel in their problems relating to prevention and control of insect-borne diseases.

The laboratory continued to provide office space for the traveling representatives of the Pan American Sanitary Bureau in charge of the sector of the Caribbean and the Gulf until June 5, 1943. Their headquarters have since been moved to Guatemala City, a location more central to their activities. During the year the laboratory staff examined for the bureau 4,031 thick-blood films for parasites. Of that number, 2,670 were from the Republic of Panama, 1,310 from Guatemala, and 51 from the Dominican Republic. The results of the examinations were reported to representatives of the bureau but cannot be analyzed here.

Cooperative services to other organizations have been continued. Frequent contacts have been made with the United Fruit Co., although we have been unable to benefit as much as formerly from the relations maintained with that organization. The United States Rubber Development Corporation has called upon us from time to time since May 1943 for surveys and advice in malaria control in their labor camps in this and neighboring areas. Representatives of various organizations have called to discuss problems relating to new drug sources, rubber, animal industry, repellents, larvacides, and similar subjects. Many visitors from the Western Hemisphere and several from the East have passed through Panama and paid short calls and exchanged ideas. These have included representatives from the office of the Coordinator of Inter-American Affairs, the Rockefeller International Health Board, the United States Public Health Service, the National Research Council, and some military organizations of the United States and Great Britain.

The auditorium of the laboratory continues to be used by a number of groups for their regular or special meetings. Included in these groups are the National Medical Association of the Republic of Panama, the Medical Association of the Isthmian Canal Zone, the Panama Canal Natural History Society, and various military medical

and sanitary organizations. The post-graduate courses in medicine for the members of the profession in Panama are given at the laboratory. At stated meetings, scientists traveling north or south are frequently available for lectures.

Snake census.-The snake census of Panama started in 1929 and has been continued as opportunity in connection with other field investigations has occurred. The work is being conducted by the Gorgas Memorial Laboratory in cooperation with Dr. E. R. Dunn, of Haverford College and the Academy of Natural Sciences of Philadelphia, and the Museum of Comparative Zoology at Harvard College. During the past year no effort has been made to collect from regions that are already well represented by large receipts. It is still necessary to explore certain regions along the Atlantic coast and most of the midlands and mountains. These regions are thinly populated and collections are difficult to make. The report_given here covers the period from September 18, 1942, to September 4, 1943. The total receipts for that period were 306 specimens of which 36 (11.7 percent) were of some poison species. Most of the catch came from the mountains of Chiriqui province and poison snakes are not very abundant in that region as compared to the lowlands. The census continues to show that the great majority of poison snakes belong to some species of Bothrops (78.6 percent). The value of the snake census has been very greatly enhanced this past year because of the need of the military forces for such information. This is particularly true in the case of mobile units. Local military organizations have had the use of embalmed specimens and a number of lectures on snake bite prevention and treatment have been given. The 15 species of poisonous snakes represented in our cumulative census up to the end of the period under review are given in the list that follows:

1. Fer-de-lance: Bothrops atrox is the most abundant of the poisonous snakes and forms the greatest medical hazard. Practically all snake bite accidents in which it has been possible to secure the snake for identification have been caused by this snake.

2 and 3. Hog-nosed vipers: Bothrops lansbergii on the Pacific side and Bothrops nasutus on the Atlantic side of the country.

4, 5, and 6. Tree vipers: Bothrops schlegelii is common all over the country and even up to altitudes of 4,000 feet but it is more common in the coastal plains and up to 1,000 feet of elevation. Bothrops lateralis and Bothrops nigorviridis nigroviridis have been, thus far, all taken from the coffee plantations at about 3,000 to 4,000 feet in elevation.

7. Godman's viper: Bothrops godmani, a ground species, is also found along the river banks in the coffee levels of Chiriqui Province. We have no collections from other mountain regions except the full length of the Chagres River and none were found in that valley.

8. Mano de piedra, timbo or jumping snake: Bothrops nummifera is represented by only two specimens and these were taken at elevations from 2,000 feet.

9. Bushmaster: Lachesis mutus is the largest viper in the collection. It is most common in the rocky forested regions but will be found also in lowland plantations where rodent life is abundant enough to serve as food. It is of very low incidence as compared to the fer-de-lance. 10, 11, 12, 13, and 14. Coral snakes: Micrurus nigrocinctus nigrocinctus is by far the most common coral species found at all levels.

Others identified in the census are Micrurus mipartitis, Micrurus dissolencus dunni, Micrurus clarki and Micrurus nigrocinctus coibensis. 15. Sea snake: Pelamydrus platurus is represented in our collection by four specimens which were all taken on land at tidewater level. They either were washed ashore or came ashore for some unknown

reason.

Dr. E. R. Dunn, in 1939, provided us with a list of other poisonous snakes that have been reported from Panama but which have thus far not appeared in our census. (See annual report for 1939.) Not all known poison-snake specimens have been given a scientific name but five specimens can be recorded: Micrurus nigrocinctus mosquitensis, Micrurus sp. from El Valle, Micrurus stewarti, Micrurus sp. from the San Blas coast, and Bothrops montecelli.

An analysis of the snake census up to date is given in the tables which follow.

TABLE 1.-Incidence of various poison species in the total census (January 1929 to
September 1943)

TABLE 2.-Incidence of poison snakes in the total census, by locations (January 1929 to September 1943)

TABLE 3.-Poison snakes in the total census, by species and locations (January 1929

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