ANTI-INFECTIOUS SERUM, 487 



in the hanging-drop. Many of the cells will be seen to be 

 perfectly motionless, while others are breaking up into 

 granules. A drop of liquid should be drawn from the peri- 

 toneal cavity at the end of 10, 20 and 30 minutes after the 

 injection. The cells are first immobilized; they then break 

 up into fragments, become granular and finally, in about 30 

 minutes, they disappear completely "like a piece of sugar 

 in water." This is "known as Pfeiffer's reaction. Exactly 

 the same condition will be observed if a mixture of the 

 serum of this animal and of the virulent cholera vibrios is 

 injected into a normal guinea-pig. If the vibrios injected do 

 not dissolve and disappear, it is conclusive evidence that they 

 belong to a different species. Furthermore, it may be stated 

 that the cholera vibrio will not disappear if injected by itself 

 into a guinea-pig, whereas harmless vibrios will dissolve. 

 The serum of the animal thus vaccinated, as stated 

 above, is anti-infectious. It will protect against the living 

 germ but not against the soluble poison. If the cholera 

 vibrio is planted in such serum it is not destroyed; it may 

 become agglutinated, but Pfeiffer's phenomenon will not be 

 seen. In other words, the serum is neither germicidal nor 

 antitoxic. 



The anti-infectious serum as indicated is not germicidal 

 in vitro, nor is it antitoxic; and yet, a small amount is 

 sufficient to save an animal from many times the fatal 

 dose of the living culture. The organisms in this case may 

 be totally destroyed in less than 30 minutes. It may be, 

 as , Pfeiffer believes, that this small amount of serum is 

 converted in the body into a germicidal substance but it is 

 more probable that this serum acts by stimulating the 

 white blood cells and other phagocytic elements, which 

 then give off the peculiar products that induce the Pfeiffer 

 phenomenon. 



It may be incidentally stated that the antitoxic serum 

 likewise possesses no germicidal properties. It is supposed 



