1908.] The Life-history of Trypanosoma equiperdum. 297 
rats before the life-cycle in the parasites has reached the point at which the 
interaction between the extra-nuclear centrosome and the nucleus occurs, and 
here also it is found that after death no changes take place in the trypano- 
somes other than those related to their degeneration, or in any way corre- 
sponding to the formation of the latent forms. 
Still further, we have at various periods of the infections abstracted blood, 
and watched the condition of the parasites until degeneration is becoming 
general, and in these cases also have encountered nothing comparable to the 
changes we have described in relation to the formation of the latent bodies. 
The change is thus related to a particular stage of the development of the 
trypanosomes in the blood. 
It will be remembered that the formation of the latent bodies in 7’. gambiense 
takes place at, and immediately after, the periods of maximum number of the 
parasites in the blood, and the immergence from the latent bodies once more 
occurs a considerable time later. The infection with TZ. equiperdum in 
rats only progresses to a first maximum, during which the rat dies. We 
find also that it is only in those rats which have resisted the infection for a 
sufficient period that the formation of latent bodies in large numbers takes 
place. It should, however, be pointed out that, even on the second day after 
the appearance of the trypanosomes in a rat infected with dourine, a few 
trypanosomes with club-shaped projections, and a few latent bodies with 
their long, fine flagella, may occasionally be encountered. This corresponds to 
the occasional appearance of latent bodies during almost all the periods in an 
infection of 7. gambiense. 
It would be extremely interesting to ascertain what exactly happens during 
the successive periods of maxima and minima, which succeed one another 
when a horse is infected with dourine; but we have found that even at the 
maxima of such infections the parasites are so few in number as to render it 
practically impossible to utilise horses for this object. 
It would seem, then: that during the infection of rats with dourine, that is 
to say, with a form of trypanosome which under normal circumstances is not. 
related to two distinct hosts, there exists a life-cycle among the parasites 
closely analogous to that occurring during the successive positive and negative 
periods of infection of the same animals with 7. gambiense. 
The parasites, after introduction into a rat, multiply by longitudinal 
fission, accompanied by amitotic division of the nucleus. After this process, 
an interaction takes place between the extra-nuclear centrosome and the 
nucleus (sexual stage ?). Division again proceeds, and finally the trypano- 
somes are converted into round bodies, which correspond to the latent bodies 
of 7. gambiense, but possess two long and delicate flagella. 
2 kB 
