METHOD OF EXAMINATION IN TRYPANOSOMA INFECTION 555 



it to move about freely and actively in the body fluids where is has 

 its usual habitat. 



While the protoplasm of the trypanosome shows a certain amount 

 of contractility, its motion is almost exclusively due to the undulating 

 membrane and the flagellum, and it is in the direction to which the 

 free whip-like filament points that the organism moves. For this 

 reason the end from which the free flagellum projects is generally 

 called the anterior extremity. A few species of trypanosomes have 

 a free flagellum at each end, but this is an exceptional occurrence 

 among these flagellata. In addition to the structures described the 

 protoplasm of trypanosomes shows larger, smaller, and very minute 

 granules, which exhibit special staining properties, and which are 

 often arranged in rows or striae; occasionally clear open vacuoles are 

 seen in their posterior part. 



From the foregoing description it may be inferred that these 

 animal microorganisms, though unicellular -and parasitic, show a 

 high degree of differentiation into a number of morphologic com- 

 ponents. When trypanosomes multiply they do so by a longitudinal 

 splitting. The micro- and macronucleus divide first, and the process 

 of splitting then generally extends to the protoplasm, the undulating 

 membrane, and the flagellum. The macronucleus, however, never, like 

 the nuclei of most of the cells of higher plants and animals, shows 

 the formation of karyokinetic figures, but it divides amitotically, 

 that is, by direct division. 



Habitat. The usual habitat of the trypanosomes is the blood of 

 vertebrate animals. In certain diseases they are also found in the 

 lymph and in the cerebrospinal fluid. They are, as far as is known, 

 strict parasites which can only exist and multiply within another 

 living host. There is no evidence that trypanosomes are ever found 

 free in the outside world. Unlike the hemosporidia of malaria and 

 the piroplasma of Texas fever, trypanosomes do not invade and live 

 inside the red blood corpuscles, nor do they engulf into their own 

 protoplasm and digest the erythrocytes of the blood of their host, 

 as, for instance, the amebse of dysentery do. They simply float 

 about in the blood plasma and derive food for existence and multi- 

 plication by processes of osmosis. WTiile trypanosomes have been 

 found in the blood of many types of vertebrate animals, such as 

 batrachians, reptiles, fishes, birds, and mammals, nothing would 

 be more erroneous than to consider all of them dangerous disease- 

 producing parasites. Quite to the contrary, most trypanosomes so 

 far discovered are harmless blood parasites and apparently no more 

 dangerous to their host than many of the bacteria which inhabit the 

 integument, the gastro-intestinal and the genito-urinary tract of the 

 higher animals and man as commensales. 



Method of Examination in Trypanosoma Infection. Demonstration 

 of trypanosomes in infected animals is, as a rule, a very easy matter, 

 although they are sometimes so scanty that it may be necessary to 



