333 



at a time when trypanosomes are decreasing in the 

 blood, the majority of trypanosomes are disintegrated 

 into a mass of debris, but some become rounded and 

 encysted (Moore and Breinl). 



Latent Forms. During the course of an infection 

 when trypanosomes are decreasing in the blood, Moore, 

 and Breinl describe forms found at first in the lungs 

 and somewhat later in the spleen and bone marrow 

 (and in small numbers in the blood), which they call 

 latent forms. They are minute forms consisting of 

 a nucleus with an intranuclear body (centrosome) and 

 a vesicle, the whole lying in a thin film of protoplasm. 

 These exist, then, in the organs (a few also in the blood) 



Fig. 106 



when trypanosomes are absent from the blood, and 

 some of these give rise again to young, and then full- 

 grown trypanosomes which multiply by longitudinal 

 division as described above. Trypanosomes thus 

 appear to have, at least in the case of a rat infected 

 with T. gambiense, a regular cycle in the body. It is 

 possible that these minute forms are the source of 

 infection in blood which, although filtered, is still 

 infective. 



Involution Forms. These are the amoeboid 

 forms of some observers. They have lost their 

 flagellum and are found under various unfavourable 

 conditions, e.g., in the blood of animals under treatment 

 with atoxyl, etc., also in the spleen (Fig. 106), or in 

 blood that has been heated to 40 for one hour, or 

 in post-mortem blood. 



