AGGLUTINS 13 



introduced, the cells produce what are called antibodies, which secure 

 immunity. The antibody (anticomplement) may have a dominating 

 affinity for the complement, unite with it and prevent the union of the 

 complement with the amboceptor ; or it may unite, in the same way, 

 with the amboceptor and prevent its union with the receptor, when it 

 is called the anti-immune body. In either event it protects the cell 

 from the alexin. 



Figure 1 1 shows the antibody (anticomplement) united with the 

 alexin, preventing a union of the alexin with the amboceptor. Figure 

 12 shows the antibody (anti-immune body) united with the amboceptor, 

 preventing a union of the alexin with the receptor. 



Precipitins. It is possible to produce, in an adapted animal, sub- 

 stances known as precipitins ; and these have been used as tests for 

 different kinds of blood. The blood-serum of an adapted animal, if 

 added to the blood used in adaption, produces a copious precipitate, 

 which does not occur with other mixtures. 



Agglutins. When the blood of an animal is adapted to the red 

 blood-corpuscles of an animal of a different species by repeated intra- 

 peritoneal injections, the blood-serum of the adapted animal becomes 

 agglutinative, not only for the blood-cells, but for other cells as well, 

 belonging to the animal whose blood has been used in the process of 

 adaption ; but no agglutination occurs in cells from other sources. This 

 process of agglutination, however, is not protective. 



