504 
ZOOLOGY: R. ERDMANN 
THE LIFE CYCLE OF TRYPANOSOMA BRUCEI IN THE RAT 
AND IN RAT PLASMA 
By Rh. Erdmann 
OSBORN ZOOLOGICAL LABORATORY. YALE UNIVERSITY 
Presented to the Academy, August 5, 1915 
It is well known that Trypanosoma brucei does not appear in the 
peripheral circulation until about forty-eight hours after inoculation. 
The actual history of the organism during this period has not yet been 
established for Trypanosoma brucei; and in other trypanosomes, in 
spite of numerous investigations, it has not been fully elucidated (cf. 
Minchin,^ and Carini^). It has been impossible to study the uninter- 
rupted hfe history of the trypanosome in the mammahan host. 
The method of cultivating Trypanosoma lewisi outside the mam- 
mahan host was first discovered by Novy and McNeal in 1903.^ Mc- 
Neal^ states that Trypanosoma brucei changes its form in the culture 
medium into round bodies which are not capable of causing infection • 
in the rat. Laveran and MesniP show four stages of this transformation 
of trypanosomes into round bodies in a medium of serum and horse blood. 
These authors term these forms "mis en boule" and believe that they are 
capable of starting a new infection and that they are comparable, when 
submitted to unfavorable conditions, to the 'latent bodies' found by 
More and Breinl^ in Trypanosoma gambiense and later in Trypanosoma 
equiperdum and Trypanosoma lewisi.'^ These mammalian trypano- 
somes showed, according to these authors, cyclical changes in the num- 
ber of trypanosomes in the host and the periodic appearance of the 
'latent bodies.' Thus there are periods in which many trypanosomes 
are in the peripheral blood and periods in which few or none can be 
discovered. These round forms have never been seen in the mammalian 
blood in Trypanosoma brucei, but only in the above mentioned culture 
media. 
For the purposes of the present study, which demand a continued 
control of the trypanosomes in culture which is not possible by culti- 
vation in test tubes, I have cultivated Trypanosoma brucei in rat 
plasma on shdes, using the tissue-culture methods of Harrison, Burrows, 
and Walton.^ The plasma was either inoculated with the trypanosomes 
themselves or used as a medium for the growth in vitro of various in- 
fected tissues of the host. In the plasma of the rat I have been able to 
keep the trypanosomes in a normal condition for an indefinite period, 
whereas by the use of Ringer's fluid or blood bouillon the organisms die 
after a few days.^ 
