IMMUNITY AND SUSCEPTIBILITY 707 



place. The complement will not combine with the cells under any 

 circumstances unless amboceptor is present and has first combined 

 with the cells. It is probable in a given serum or body fluid that there 

 are several complements which may activate a variety of amboceptors. 

 However, it has been shown that the same complement will activate 

 a variety of amboceptors of certain kinds. 



While the majority of lytic sera are thermolabile some have been 

 noted which are thermostable to a certain degree. Hamilton has de- 

 scribed such a serum resulting after immunizing animals to Bact.' 

 pseudodiphthericB and Horton has noted thermostable substances in 

 normal rat serum which are lytic for Bact. anthracis. 



Various sera have Seen noted which possess amboceptors for 

 certain cells but are not lytic because they do not possess the necessary 

 complement. For example, the serum of the dog contains amboceptors 

 for Bact. anthracis but no complement. If in this instance a foreign 

 complement such as that in guinea-pig or rabbit serum is added there 

 will be lysis of the bacterial cells. 



Occasionally the absence of complement is of benefit to the animal 

 in question and may account for the seeming natural immunity. For 

 example, the venoms of the poisonous snakes are nothing more than 

 amboceptors and when these substances are injected into an animal 

 body such as a hog, which does not possess the required complement, 

 no lysis of the body cells takes place. On the other hand, should the 

 animal, such as a rabbit or man, possess the necessary complement, as 

 they do, lysis will take place. 



Substances are sometimes present normally in sera which have 

 the power of combining with the amboceptors which may be present, 

 and prevent the latter from combining with the cells so that when the 

 complement is added there will be -no lysis. Such substances must be 

 designated as antiamboceptors. These antiamboceptors (antiantibodies) 

 may be developed in an animal by immunization with amboceptors 

 of definite kinds. There are other substances which may also engage 

 the amboceptors which cannot be called amboceptors in the true sense 

 but they accomplish the same purpose and are, therefore, classed with 

 these bodies. 



The Deviation of the Complement. The complement may be deviated 

 in several ways and as a result lysis of the cells in question may be 

 prevented. 



