66 COLLECTED STUDIES IN IMMUNITY. 



the binding group of the latter against any further combination with 

 complement. If, on the contrary, the anti complement combines 

 with the haptophore group of the complement, the interbody is 

 left free and must therefore still be capable of reactivation. The 

 experimental solution of this question was very easy. The erythro- 

 cytes, loaded with interbody, were subjected to the action of a 

 mixture of complement and anticomplement which had been neu- 

 tralized to complete inactivity. After centrifuging it was found that 

 the blood-cells dissolved readily on the further addition of comple- 

 ment. Solution also occurs if a small amount of complement in 

 excess is added to the exactly balanced mixture of complement and 

 anticomplement. These experiments indicate that the anticomple- 

 ment acts by fitting into the haptophore group of the complement and 

 side-tracking this group. 



We have also convinced ourselves that it is possible to produce 

 anticomplements not only with horse serum but also with other 

 sera, such as the sera of goats, dogs, cattle, rabbits, and guinea-pigs, 

 by injecting the serum into foreign species. In these experiments the 

 choice of animals employed for purposes of immunization also plays 

 an important role. For example, a rabbit treated with goat serum 

 very readily yields an anticomplement, whereas when a dog was 

 similarly injected no anticomplement (at least in the two cases 

 examined by us) could be demonstrated. So far as we were able 

 to determine, the protection afforded by the anticomplement extends 

 to all the species of blood-cells on which the serum used for immuni- 

 zation exerts its action. Since the sera in question, so far as lysin 

 action is concerned, contain a plurality of complements, the anti- 

 complementary serum must contain a whole series of anticomple- 

 ments which correspond to the different complements present in 

 the immunizing serum. Perhaps this poly valence of the anticom- 

 plementary serum accounts for the phenomenon that certain anti- 

 sera produced by means of a particular blood serum are able to 

 inhibit the injurious action of many other kinds of blood serum. 

 These facts indicate that this interchange of protection is due to 

 the presence in the two sera of a certain number of common com- 

 plements. In fact there seem to be cases in which certain species 

 have the majority of their complements similar. Such a case in 

 all probability is that of the goat and the sheep, as is evidenced by 

 the fact that in the reactivating action goat serum can be completely 

 replaced by sheep serum and vice versa. This at least is true for 



