856 



IMMUNOLOGY 



following: a subnormal condition of the rats or infections, such as 

 Bartonella or paratyphoid. In any case Culbertson and Wotton (1939) 

 have found that fatal infections develop in rats in which the content of 

 ablastin is low. 



Early investigators (Rabinowitsch and Kempner, 1899; von Wasie- 

 lewski and Senn, 1900; especially Laveran and Mesnil, 1901; MacNeal, 





E200- 

 o 



c 

 o.1iO- 



Dau of Infection 



Figure 189. The changes in number of Trypanosoma lewisi and the coefficient of 

 variation and percentage of division forms during the course of infection in rat 105. 

 As acquired immunity develops, the rate of reproduction is inhibited by ablastin, as 

 evidenced by the low coefficient of variation and low percentage of division forms be- 

 ginning at location 1, and the parasites are killed by trypanolysins operative at locations 

 2 and 3. Whether, in addition, natural immunity operates has not been ascertained. 

 (From W. H. Taliaferro, 1924; division forms added.) 



1904; W. H. Brown, 1915) were convinced by their microscopical 

 studies that T. lewisi reproduces only during the first few days in the rat, 

 after which the trypanosomes live in the blood as nonreproducing adults. 

 This conclusion has been substantiated by W. H. Taliaferro (1924), 

 Coventry (1925), and Regendanz and Kikuth (1927). Thus in Figure 

 189 the coefficient of variation of the total length of the trypanosomes 

 and the percentage of division forms, each of which, as will be recalled, 

 measure the rate of reproduction, are high when trypanosomes appear 



