130 ANIMAL PARASITES. 



cently succeeded in the artificial culture of the Trypanosoma lewisi of the 

 wild rat ' aud of T. brucei of the tsetse-fly disease. 2 



Cercomonas intestinalis is a pear-shaped, flagellate structure (Fig. 54), 

 about 0.012 mm. long, making, when alive, rapid movements. It has 

 been found in the evacuations of persons suffering from cholera, typhoid 

 fever, and diarrhoea. 



Trichomonas vaginalis has an oval or pear-shaped body from 0.015 to 

 0.025 mm. long, with a cluster of flagella at one end and an undulating 



FIG. 53. TRYPANOSOMA FIG. 54. CERCOMONAS INTESTINALIS. FIG. 55. TRICHOMONAS VA- 

 LEWISI. After Braun. GINALIS. After Dock. 



membrane, frequently mistaken for cilia, upon the side (Fig. 55). It is 

 of occasional occurrence in vaginal exudates. The possibility of mistak- 

 ing the T. vaginalis for human spermatozoa should be borne in mind in 

 medico-legal examinations, although to an observer familiar with either 

 structure such a mistake could hardly occur. 



Some forms of Trichomonas have been found in the urine of men, in 

 the intestines, and in the sputum. 3 



III. SPOROZOA. 



The sporozoa are all parasitic, living at some period of their life 

 cycle in the cells of their host, and are especially characterized by their 

 reproduction through eucystment and spore formation. Many forms of 

 the organisms, especially the spores, are very minute and difficult of 

 identification. They are widely distributed, being found as parasites in 

 nearly all classes of animals. They may invade the gastro-intestinal 

 canal and the kidney and their adnexa, the blood, muscle, connective 

 tissue, and skin. While many of them appear to be harmless to their 

 host, others may do serious damage by blocking the tissue spaces and 

 thus, or in other ways, inducing necrosis, atrophy, or cell death. Some 

 forms are wholly intracellular, others remain for only a part of their life 



1 For a resume of trypanosomatic infections and the methods of artificial culture of 

 protozoa, see McNeal and Novy, in " Contr. to Med. Research, Vaughan Anniversary 

 Volume," 1903, p. 549; for discussion of trypanosomiasis in man, sceManson, Brit. Med. 

 Jour., Sept. 19th, 1903, p. 645; for a study with bibliography of Trypanosoma lewisi, 

 see Francis, Bull. No. 11, Hygienic Laboratory, Public Health and Marine Hospital 

 Service, U. S. A., 1903. For a study of trypanosomiasis with special reference to ser- 

 vice in the Philippine Islands, see Musgrave and Clegg, Department of Interior, U. S. A., 

 Bureau of Government Laboratories, 1903. 



2 Novy and McNeal, Journal of Infectious Diseases, vol. i., 1903, p. 1. 



3 For original studies of Trichomonas with historical summary and bibliography, 

 see Dock, Am. Jour. Med. Sc., vol. cxi., p. 1, 1896. 



