4i8 



RESEARCH IN PROTOZOOLOGY 



In order to facilitate discussion, hypothetical results are indi- 

 cated. 



Table i gives a protocol for the titration of the anti-sheep-cell 

 rabbit serum which is the first reagent needing standardization. 

 Inasmuch as this is an important basic titration, the complement 

 should be standardized as far as possible (see following para- 

 graph), and hence, should consist of pooled serum from several 



TABLE I 

 PROTOCOL FOR THE TITRATION OF ANTI-SHEEP SENSITIZER 



guinea-pigs. According to the possible results, complete hemolysis 

 occurs through Tube 15 which contains 0.5 of a cubic centimeter 

 of I : 1 0,000, and therefore, the titre is i :20,ooo in the fractional 

 units or i 14000 in the standard units. Later, in using sensitized 

 cells, it is necessary to have cells and sensitizer in such a dilution 

 that each 0.5 of a cubic centimeter contains two per cent cells 

 and two units of sensitizer. This is easily done by mixing equal 

 quantities of four per cent washed sheep cells and a dilution of 

 sensitizer so that two units are contained in 0.25 of a cubic centi- 

 meter, which, in the example above, would be i 12500, in other 

 words, an equal mixture of double strength reagents. (A titration 



