166 STUDIES IN IMMUNITY. 



THE PROPERTIES OF ANTIHEMATIC SERA. 



The active serum used in our previous work was furnished by 

 guinea-pigs that had received several injections of defibrinated 

 rabbit blood. This serum has a harmful effect on rabbit corpuscles 

 in that it agglutinates them and brings about their dissolution. 

 In other words, it attacks the identical cells which have been used 

 to inject the animals that have furnished the serum. 



But it might well be imagined that such a serum also possesses 

 " defensive properties" in addition to ''attacking properties." 



Let us consider, for example, the serum of a rabbit that has been 

 injected with normal hen blood. Normal hen serum has the 

 property of agglutinating and dissolving rabbit corpuscles. It may 

 well be, then, that the rabbit that has been " vaccinated" against 

 hen blood should furnish a serum that is able, not only to attack 

 hen red blood corpuscles energetically, but also to defend rabbit 

 corpuscles against the harmful effect of hen serum. In other words, 

 our active serum might be endowed to a certain extent with anti- 

 toxic properties in addition to the antihematic property, which 

 is comparable to the antibactericidal property of cholera serum; 

 in such a case the toxin would be hen serum. We shall consider 

 these sera, then, from two standpoints, first as regards their anti- 

 hematic property and secondly as regards their antitoxic property. 



A. Antihematic property. The antihematic property is present 

 in the serum of animals treated with several injections of defibrinated 

 blood from a different animal species.* The serum of rabbits that 

 have received intraperitoneally several injections of 10 c.c. each of 

 defibrinated hen blood shows properties similar to those found in 

 the serum of guinea-pigs treated with rabbit blood. Although 

 normal rabbit serum has only the faintest agglutinating and dis- 

 solving effect on hen red blood corpuscles this active serum agglu- 

 tinates and dissolves them energetically. This action, however, is 



* Rabbits that have received six intraperitoneal injections of 10 c.c. of defibri- 

 nated rabbit blood show no particular property in their serum. This is reasonable 

 enough. The production of the active substances found in serum is evidently due 

 to a stimulation of the cells in the animal body on the introduction of foreign 

 substances not normally present, which may have some effect on the cell, or, 

 in other words, which may lead to a change in the chemical or physical constitution 

 of the cell. 



