334 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



of a rabbit, they are not dissolved; they are deposited little by little 

 in the bottom of the tube; the hquid floating on the surface becomes 

 clear and colorless. But if these same red blood corpuscles of the 

 sheep are introduced into dog serum, they do not fall to the bottom 

 of the tube; they are destroyed, and the liquid becomes uniformly 

 red and translucent. Buchner attributed this haemolysis to a normal 

 soluble principle named alexin (Buchner) or complement (Ehrlich). 



Bordet has provoked artificially in the blood of the rabbit the forma- 

 tion of a haemolytic serum capable of dissolving the red blood cor- 

 puscles of the sheep. Having made four injections of red blood cor- 

 puscles of sheep into a rabbit, separated by intervals of 8 days, he 

 determined that, 5 days after the last injection, the rabbit serum had 

 acquired the power of haemolysis of the corpuscles of the sheep. 

 Bordet then demonstrated that haemolysis is specific. For example, 

 the serum of a rabbit immunized with the corpuscles of a sheep dis- 

 solves only the corpuscles of the sheep; the serum of a rabbit im- 

 munized with the corpuscles of the horse dissolves only the corpuscles 

 of the horse, etc. 



These experiments show that there can be created artificially a 

 specific defense of the organism, that is to say, directed not only against 

 the bacteria but even agamst an alien cell. Bordet has demonstrated 

 also that haemolysis results from the combined action of two sub- 

 stances which he calls alexin and sensibilisatrice or amboceptor. 

 While alexin is fragile and destroyed by heating at 55°, the sensibilisa- 

 trice is destroyed only by heating at 60°-65°. The first-named pre- 

 exists in the normal animal; the second, specific, is lacking in the 

 normal animal. It originates in the organism into which alien cells 

 have been introduced. 



Alexin, while being in principle able to destroy an alien cell, is in- 

 capable of fiUing this rule by itself alone, because it does not have the 

 power to do so. The sensibilisatrice plays the role of intermediary, 

 of mordant; it fixes itself on the alien cell and permits the alexm to 

 exercise its own destructive action. Alexin is a normal defensive 

 principle that is found in the blood of men and animals. Capable 

 of combating the enemies invading the organism, without any dis- 

 tinction, in particular the bacterial pathogens, it has to be aided by 

 the specific sensibilisatrice. This is secreted automatically by the 

 organism when it is invaded by an aUen cell or by an infectious agent. 



The microbic invasion of an organism either experimentally or by 

 disease provokes in the organism the elaboration of properties some- 

 times dissolving, sometimes agglutinating, sometimes both. Bacte- 

 riolysis is specific. The production of it can be determined experi- 

 mentally by the inoculation of the animal with weak microbes. 



We have seen that in these experiments Pfeiffer had determined the 

 agglutination and the granular degeneracy of the cholera vibrios in- 

 jected into the peritoneum of an immunized guinea pig. The same 



