INTEKNAL SECRETIONS OK HOEMONES 413 



or bacterilytic body, often called the amboceptor requires the 

 co-operation of another body to enable it to. act, and this 

 body has been called the complement or activator. Ehrlich 

 supposes that the immune body does link to the protoplasm 

 of the organism, but that it must in its turn be linked to the 

 complement. The figure may help to explain this (fig. 167). 



Cytotoxins. Similar anti-bodies, acting upon the cells of 

 the animal body, may be produced by injecting the particular 

 kind of cell into an animal of another species. Thus, if human 

 blood be repeatedly injected into a rabbit the serum of the 

 rabbit's blood becomes hcemolytic i.e. acquires the power of 

 dissolving the erythrocytes in human blood. In this case too, 

 the immune body requires the presence of a complement, 

 readily destroyed at a comparatively low temperature, to enable 

 it to act. If such hsemolytic serum be injected into another 

 animal an anti-hsemolysin may be developed a body which 

 will antagonise the action of the hsemolysin. Possibly this is 

 a body which links with the amboceptor to prevent its linking 

 to the complement. 



Preeipitins. By the injection of the proteins of the blood 

 of any particular animal into an animal of another species a 

 serum is developed which precipitates the proteins of the blood 

 of the first species and of no others. 



In these various cases the active body is produced by the 

 throwing off of side-chains from protoplasm, and as these 

 products are carried away in the blood the process is exactly 

 analogous to the formation of internal secretions. 



Opsonins. Many bacteria after treatment with the serum of 

 the animal are taken up by the leucocytes, but if not treated 

 with serum are not taken up. Apparently the serum contains 

 something which has been called an opsonin which prepares 

 the bacteria to be devoured. The action of opsonin s is destroyed 

 by temperatures between 55 and 65 C. The opsonic power of 

 the serum is often increased by the injection of small quantities 

 of dead bacteria (Vaccines). 



