JOURNAL OF ACRICDLTDRAL RESEARCH 
Vol. XIV Washington, D. C., September 23, 1918 No. 13 
AN IMPROVED METHOD FOR RECOVERING TRYPANO¬ 
SOMES FROM THE BLOOD OF RATS FOR ANTIGEN 
PURPOSES IN CONNECTION WITH COMPLEMENT 
FIXATION 
By F. H. Reynolds and H. W. Schoening, Pathological Division , Bureau of Animal 
Industry, United States Department of Agriculture 
UNDESIRABLE FEATURES OF METHODS IN USE 
Up to the present time the methods employed in recovering try¬ 
panosomes from the blood of artifically infected rats, though quite sat¬ 
isfactory, have presented some features which were somewhat detrimental 
to the antigen and which, if overcome, would greatly improve the same as 
to purity and, obviously, specificity. The question of suitable and 
sufficient antigens being one of vital importance, more especially in this 
laboratory, where many thousands of fixation tests for dourine are per¬ 
formed annually, it was desirable to seek an improvement. 
Watson 1 describes a method whereby the trypanosomes might be 
recovered in large quantities from the blood of infected rats killed at the 
height of the disease. It was essentially a method of repeated centri¬ 
fuging, as the erythrocytes, being of greater specific gravity than the 
trypanosomes, necessarily settled to the bottom. However, the method 
had its faults, in that many of the organisms would be drawn down with 
the red cells and it was necessary to sacrifice many of the trypanosomes 
to prevent the presence of too great a quantity of red cells in the antigen. 
Therefore it was necessary to eliminate the following undesirable features: 
First, however careful and painstaking one might be, it was quite impossible 
to collect all the trypanosomes present in the blood; second, it was im¬ 
possible to procure a pure antigen totally devoid of rat erythrocytes 
which, when present in large numbers, would tend to decrease the 
antigenic value as well as the keeping qualities; third, it was a laborious 
process consuming half a day, and, as experience has shown that subjec¬ 
tion to room temperature greatly impairs the antigenic value, the neces¬ 
sity for its rapid preparation and early storage on ice is quite apparent. 
Even then it was quite impossible to procure a pure product. There- 
1 Watson, E. A. dourine and the complement fixation test. In Parasitology, v. 8, no. 2, p. 
156-183. 1915. 
Journal of Agricultural Research. 
Washington, D. C, 
pi 
Vol. XIV, No. 13 
Sept. 23,1918 
Key No. A-42 
(573) 
