116 COLLECTED STUDIES IN IMMUNITY. 



by horse serum but is reactivated by goose serum, we should neces- 

 sarily have to conclude that "the " complement of the goose is much 

 more closely related to " the " complement of the rabbit than is 

 that of the horse. From the Unitarian standpoint also a more 

 marked difference should be manifested by the complements of 

 the goose, the chicken, and the pigeon, for the first two reactivate 

 the immune body, while the last does not. A priori, therefore, the 

 Unitarian view is very improbable ; but aside from this the reactivat- 

 ing experiment with the goose immune body (which shows this to 

 be reactivated by all three avian sera) speaks against this view. 



All of these facts are readily explained if we accept the pluralistic 

 view that each serum contains a large number of complements, and 

 that certain types have a wide distribution in many classes of animals. 

 In these they may be completely similar, or, what is of primary impor- 

 tance, their haptophore groups may be identical. It may very 

 well be that the avian sera are alike in the greater part of their partial 

 complements, and that therefore all three sera may in certain cases 

 e.g., with the immune body of a goat immunized, with ox blood reactivate 

 in like manner. But it is not necessary that these three species 

 correspond in all their complements, and so it may happen that a 

 certain partial complement which is absent in pigeon serum is present 

 in the other sera. This occurs in the above case with the immune 

 body of the rabbit immunized with ox blood (and with that of the 

 goat similarly treated). 



I should like to emphasize one more point. The immune body 

 of the rabbit immunized with ox blood is not reactivated by pigeon 

 serum, whereas the immune body of the goat immunized with ox 

 blood is thus reactivated. This fact in itself should occasion no sur- 

 prise whatever. The tissue receptors which are present in the avian 

 organism, and which constitute the matrix of the amboceptors in 

 question, possess complementophile groups that fit complements 

 widely distributed throughout the avian body. It is not at all remark- 

 able, therefore, that the immune body obtained from the goose finds 

 complements in various avian sera. In like manner it can readily 

 be understood why pigeon serum is unable to reactivate the immune 

 body of the rabbit immunized with ox blood. 



The general conclusion, however, that the avian complements in 

 their entirety are different from those of mammals, cannot be drawn 

 from this, as is shown by the reactivation of the rabbit immune 

 body by goose and chicken sera. 



