TRYPANOSOMA LEWISI 467 



Before it has become completely detached, division may again commence 

 in the parent form, and the process may be repeated several times, so that 

 a large individual, now, however, much reduced in breadth, with several 

 small ones not completely separated, may occur (Fig. 197, 4-9). These 

 small forms detach themselves, and may in turn divide more or less 

 equally (Fig. 197, lo-ii). On the other hand, the small forms may 

 become round, and, while increasing in size, the kinetoplast divides 

 repeatedly, together with the nucleus, the division of the latter being 

 always a little behind that of the former, while new axonemes grow out 

 from the newly-formed kinetoplasts. Cytoplasmic bodies are in this way 

 produced which have 2, 4, 8, or 16 nuclei and kinetoplasts, and a corre- 

 sponding number of axonemes and flagella (Fig. 197, 6-7). The nuclei 

 are peripherally arranged, and the body becomes indented between the 

 nuclei, and finally segmented into a number of organisms, which resemble 

 the round parent form from which they were derived. Eventually, these 

 small individuals elongate and become transformed into the trypanosome 

 forms. The multiplication forms gradually disappear from the blood, and 

 are replaced by the typical trypanosomes, which appear no longer to 

 multiply. During the multiplication phase the various forms met with 

 are referable to the types described, but all intermediate stages between 

 these are met with, and a blood-film made at this period shows a wonderful 

 series of organisms belonging to the various leishmania, leptomonas, 

 crithidia, and trypanosome types described above. The origin of the 

 large trypanosomes which commence the reproductive phase is doubtful. 

 It is probable that they are the result of growth of the inoculated forms, 

 which are those which occur in the late phase of an infection. 



Reaction to Sera. — Laveran and Mesnil (1901a) first demonstrated 

 that the serum of rats which had acquired immunity to T. lewisi after 

 recovery from an infection had a marked agglutinating effect on the 

 trypanosomes if blood containing them were mixed with the immune 

 serum. In a few minutes the trypanosomes attached themselves to one 

 another by their posterior ends, producing finally clumps of organisms 

 (Fig. 152). The trypanosomes in these clumps are quite active, and the 

 condition of agglutination may pass off, the individual trypanosomes 

 swimming away. In other cases, if the agglutination persists, the trypano- 

 somes eventually cease their movements and degenerate. There is 

 evidence which indicates that two distinct substances are involved — an 

 agglutinin and a trypanolysin. In some instances an auto-agglutination 

 has been observed in the blood of infected animals. According to Talia- 

 ferro (1923, 1924), the serum of rats in the late stages of an infection 

 contains a substance which inhibits the development of the trypanosomes. 

 If 2 c.c. of such a serum is mixed with washed trypanosomes and injected 



