DEVIATION OF COMPLEMENT 149 



complement in association with the homologous serum may 

 be retained. 



We therefore conclude that (1) when a precipitate forms, 

 the deviating property is contained in it, and may be so 

 exclusively; on the other hand, (2) the deviation pheno- 

 menon may occur without precipitation, and (3) the amount 

 of deviation is not always in proportion to the amount of 

 precipitate. The last-mentioned fact would indicate, as 

 Moreschi suggests, that the precipitate has not always the 

 same composition, and possibly the precipitin and the 

 precipitinogen unite in varying proportions. 



5. THE DEVIATION OF COMPLEMENT AS REGABDS 

 SPECIFICITY 



The important practical question, with regard to the 

 deviation of complement, is the same as in the case of 

 precipitins, and concerns the possibility of distinguishing 

 different kinds of bloods, or rather sera. We have carried 

 out a number of observations on this subject, though these 

 must be regarded as of a preliminary nature, and a much 

 more extended series will be necessary. Using an anti- 

 numan serum, we have tested the sera of various animals 

 with it, and observed whether there was any deviation of 

 rabbit's complement (ox's corpuscles treated with immune- 

 body from the rabbit being used as the indicator). We 

 have obtained purely negative results with the sera of the 

 ox, sheep, pig, dog, cat, mouse, guinea-pig, horse, and 

 pigeon. In each case 0-05 c.c. of the anti-serum was used 

 along with as much as 0-01 c.c. of the serum to be tested : 

 in every case as much complement was found to be free as 

 when the anti-serum was used alone. In the case of the 

 primates, however, distinct deviation of complement was 

 obtained. With the serum of a chimpanzee, for which 

 we are indebted to Prof. Woodhead, the following are 



