562 IOWA DEPARTMENT OF AGRICULTURE 



as in the specific bactericidal serum. For this reason, if bactericidal 

 serum is rendered inactive by being warmed to 55 degrees C, it can be 

 reactivated by serum, from a normal animal. The less stable constituent 

 of bactericidal serum which is found in normal serum is known as the 

 complement. The other which is stable and found only in specific serum 

 is termed amboceptor. The ferment-like action, or digestive action 

 of the complement cannot injure the bacterial cell until the cell has been 

 rendered susceptible to the action of the complement by the amboceptor. 

 The complement which possesses the digestive power decomposes on 

 standing and does not exist in immune serum unless it is perfectly 

 fresh. This explains why bacteria are not dissolved by bactericidal 

 serum after it has stood for some time; also why it may be reactivated 

 by adding a little fresh normal serum, or by injecting it into the living 

 animal. It also explains why a serum may be inactive in test tube ex- 

 periments and intensely active in the living body, in which it finds the 

 complement necessary for its action. 



The amboceptor, or immune body as it is sometimes called, possesses 

 two binding groups, one which attaches to the bacterial cell and the 

 other to the complement of the normal serum, and it is only through 

 the immune bodies that the complement can affect the bacterial cells. 

 Therefore, the immune bodies or amboceptor is the exclusive factor in 

 the specific action of the bactericidal serum. 



A great variety of inter-bodies are found in small amounts in normal 

 serum, and in addition a considerable amount of complements. In im- 

 mune serum, on the other hand, an enormous Increase in the amount of 

 specific inter-bodies occurs which constitutes the immune bodies or 

 amboceptors. The complement is not increased by the immunizing pro- 

 cess. Only one of the necessary constituents is therefore supplied by 

 the injection of an immune serum, and that is the immune body. The 

 other necessary bodies or complements are found in the animal to be 

 treated. 



When hogs have passed through an outbreak of cholera, we speak of 

 natural acquired active immunity. When treated with serum a hog 

 acquires artificial passive immunity. When treated by the serum simul- 

 taneous method, the hog has artificially acquired active immunity. Nat- 

 urally acquired immunity is always active inasmuch as we have seen 

 that the cells of the body must take active part in overcoming the infec- 

 tion. 



If immunity in hog cholera is antibacterial, the following would be 

 in harmony. When a hog recovers from infection with hog cholera virus, 

 he will have developed during his recovery, a large number of ambo- 

 ceptors or immune bodies. If he is now treated with a large quantity 

 of virulent blood, the cells of the body would be stimulated to an in- 

 crease;! production of amboceptors which would consequently be found 

 in large numbers in the blood; the complement would not be increased. 

 If the serum is now drawn from the animal the complements soon decom- 

 pose on account of their unstable character, but the immune bodies being 

 quite stable, would remain in the serum indefinitely unless subjected to 



