252 



THE PATHOGENIC FLAGELLATES 



So perfectly have trypanosomes become adapted to mammalian 

 blood and mammalian temperatm-e, that in the majority of species 

 removal from the circulation, even if the blood be kept sterile, results 

 in loss of virulence or activity, and in death. In some cases, c. (]., 

 T. lewisi, different observers have kept infected blood for considerable 

 periods (Francis, eig'hty-one days), but in the majority of cases the 

 organisms do not remain alive for so long a time {T. hriicci or T. 

 evansi only two to three days). Even when successful such experi- 

 ments involve no multiplication processes, the organisms being merel)' 

 j^reserved alive, and with a few exceptions such appears to be the case 



' Includes T. transvaaliensis, Lav., and T. lingardi, 1^, BI. 



