4 o 



Scientific Proceedings (47). 



30 (639) 



The advantage for certain experiments in vitro of suspending 

 trypanosomes in serum. 

 By B. T. TERRY. 



[From the Laboratories of the Rockefeller Institute for Medical 

 Research, New York, and from the George Speyer House, 

 Frankfort a/M, Germany.] 

 The amount of trypanocidal substance contained in a given 

 solution is sometimes estimated in vitro by determining the degree 

 to which the solution may be diluted before it ceases to immobilize 

 the parasites. 



For want of a better diluent, trypanosomes have usually been 

 suspended in physiological salt solution (with or without the addi- 

 tion of citrate), although salt solution not infrequently immobilized 

 the parasites in 30 to 60 minutes. 



In 1910, the writer made observations which caused him to 

 substitute serum for the salt solution he had previously employed 

 in suspending T. brucei. Serum (when not bound by the medica- 

 ment under investigation) had the following advantages: 



1. The motility of the control parasites was greatly prolonged. 

 This enabled the observations to be continued over a longer time. 



2. The motility of the control parasites was accelerated. This 

 enhanced the delicacy of the tests in vitro by rendering more 

 striking the contrast between the poisoned and the non-poisoned 

 trypanosomes. 



It was found, moreover, that poisons not infrequently im- 

 mobilized more quickly trypanosomes suspended in serum than 

 they did those suspended in salt solution. This also seemed to 

 give serum a slight advantage over salt solution as a medium in 

 which to suspend trypanosomes. 



Rabbit, ox, horse, goat, sheep, pig, chicken, rat, and mouse 

 sera were tested and were found to be efficient in prolonging the 

 motility of trypanosomes. 



It soon became easy to keep on hand a large supply of serum, 

 for experiment showed that cattle serum, filtered through a Berke- 

 feld filter, bottled aseptically, and preserved in the ice-box, retained 

 its activity for many months. 



