THE AGGLUTININS 2O7 



injections of their specific antigens. They are also frequently 

 present apart from any interference. For example, normal human 

 serum clumps the second vaccine of anthrax powerfully, and in 

 most cases has a feeble action on both B. typhosus and B. coli. 

 Horse serum is very rich in agglutinins, clumping typhoid and 

 coli bacilli, the B. pyocyaneus, and the cholera vibrio, often in 

 dilutions as high as i : 100. In most cases agglutinins are present 

 in small amounts in the serum of infants and young children, and 

 become more abundant in later life. This suggests that they may 

 be formed in part, at least by a process of auto-inoculation with 

 bacteria, principally, perhaps, from the intestine. We have 

 already seen, however, that on Ehrlich's theory the presence of 

 antibodies in normal animals is readily explicable without such 

 assumption. 



The injections of bacteria or cells of any sort leads to the pro- 

 duction both of agglutinins and of cytolysins, and in most cases of 

 haemolysis or bacteriolysis agglutination occurs as the first step in 

 the process. The question arises, therefore, whether they are the 

 same substance. It is easy to show that they are not, since sera 

 which contains agglutinin do not necessarily contain immune body, 

 or vice versa. In sera obtained by artificial immunization, of course, 

 the two are almost invariably formed side by side, and it is only 

 by special processes that we can obtain the one without the other. 

 Thus Frouin claims that if dried dog's corpuscles are washed with 

 acetone and injected into a rabbit, they cause the production of 

 agglutinin ; but no haemolysin. The residue from the evapora- 

 tion of the acetone, on the other hand, yields haemolysin, but no 

 agglutinin. But in sera from normal animals it is quite common 

 to find the one without the other. Thus the serum of healthy 

 human beings frequently clumps normal human corpuscles, but 

 haemolysis is extremely rare. The converse process haemolysis 

 without agglutination also occurs ; and with regard to antibacterial 

 sera of artificial origin, Frankel and Otto found that when a dog 

 was fed on typhoid cultures it developed agglutinin, but no immune 

 body. Lastly, in many cases the action of agglutinin is destroyed 

 at a lower temperature than that of immune body, although both 

 substances are in a marked degree thermostable. We shall have 

 to discuss the effects of heat on agglutinin more fully subsequently. 



There is, as a matter of fact, a kind of antagonism between 

 agglutination and cytolysis. Cells which are crowded firmly 

 together are naturally shielded, more or less, from the solvent 



