INTERNAL SECRETIONS 



393 



into a rabbit the serum of the rabbit's blood becomes 

 hwnolytic i.e. acquires the power of dissolving the 



com 



a 



erythrocytes in human blood. In 

 this case too the immune body re- 

 quires the presence of a comple- 

 ment, readily destroyed at a low 

 temperature, to enable it to act. 



Precipitins. By the injection of 

 the proteids of the blood of any parti- 

 cular animal into an animal of another 

 species a serum is developed which 



precipitates the proteids of the blood FIG. 155. To illustrate the 



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. 



anchoring of the anti- 

 body, a, to the cell by 

 a side chain, sc, and 

 the action upon it of 

 complement, com. 



