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cytoplasm, becomes set free in the blood. These ‘ latent bodies^ as 
we have termed them, are eventually carried out of the peripheral 
circulation, and are subsequently to be found in large numbers in the 
spleen, the bone-marrow, and other organs. The process just 
described goes on until there may be no parasites to be found at all 
in the peripheral blood, but the latent bodies do not disappear, and 
after a time some of them grow larger in size, develop a new extra- 
nuclear centrosome (apparently from the division of the intra¬ 
nuclear centrosome), become flagellated, and finally gradually 
transform themselves into trypanosomes again. When this process 
has been completed, a similar cycle is passed through in relation to 
each alternating period of presence, and absence of the parasites in 
the blood, which the infected animal may present. It should be 
noted, however, that the cycle does not necessarily go forward at the 
same rate in all the trypanosomes present in an infected rat. All 
through the alternating periods there may be found a few trypano¬ 
somes at almost every stage of the cycle. 
Turning now to the development of 2 . eqiiiferdtim* it is found 
that in horses the infection presents the same sort of alternation of 
presence and absence of parasites in the blood that occurs during the 
infection of rats with T. ganibiense, but in relation to the study of 
J. equiperdum in horses a difficulty presents itself. In such 
infections the parasites are so few, that it is practically impossible to 
obtain a sufficient number of them at the various periods of the 
curve of the infection for any adequate study. 
The same is the case when rabbits are infected with Dourine. We 
have therefore utilised rats, wherein the parasites multiply very 
rapidly, the features of the disease being as follows: — 
After injection no parasites appear until about the third day. 
They then multiply with extreme rapidity, and kill the animal in 
about four days after their first appearance in the blood. In rats, 
tlierefore, there is during an • infection of Dourine only one 
developmental period, which is completed at, or about, the time of 
death of the infected animal. From the time of their first appearance 
flte parasites multiply by longitudinal division; the features of this 
process being the same as those occurring during the multiplication 
’ Salvin-Moore & Breinl. On the Life Historv of Trypanosoma equiperdum. 
Soc., 1908, Vol. go. 
