476 IMMUNITY 



the various secretions, and in these it has been found, though 

 in much less concentration than in the blood. It is present in 

 the milk, and a certain degree of immunity can be conferred on 

 animals. by feeding them with such milk, as has been shown by 

 Ehrlich, Klemperer, and others. Klemperer also found traces of 

 antitoxin in the yolk of eggs of hens whose serum contained 

 antitoxin. Bulloch also found in the case of hsemolytic sera 

 (vide infra) that the anti-substance (" immune -body ") is trans- 

 mitted from the mother to the offspring. 



Antibacterial Serum. The stages in the preparation of 

 antibacterial sera correspond to those in the case of antitoxic 

 sera, but living, or, in the early stages, dead cultures are used 

 instead of toxin separated by nitration, and in order to 

 obtain a serum of high antibacterial power a very virulent 

 culture in large doses must be ultimately tolerated by the 

 animal. For this purpose a fairly virulent culture is obtained 

 fresh from a case of the particular disease, and its virulence 

 may be further increased by the method of passage. This 

 method of obtaining a high degree of immunity against the 

 microbe is specially applicable in the case of those organisms 

 which invade the tissues and multiply to a great extent within 

 the body, and of which the toxic effects, though always existent, 

 are proportionately small in relation to the number of organisms 

 present. The method has been applied in the case of the 

 typhoid and cholera organisms, the bacillus of bubonic plague, 

 the bacillus coli communis, the pneumococcus, streptococcus 

 (Marmorek), and many others. In fact, it seems capable of very 

 general application. 



The important result obtained by such experiments is, that if 

 an animal be highly immunised by the method mentioned, the 

 development of the immunity is accompanied by the appearance 

 in the blood of protective substances, which can be transferred to 

 another animal. The law enunciated by Behring regarding 

 immunity against toxins thus holds good in the case of the 

 living organisms, as was first shown by PfeifFer. The latter 

 found, for example, that in the case of the cholera organism, so 

 high a degree of immunity could be produced in the guinea-pig, 

 that "002 c.c. of its serum would protect another guinea-pig 

 against ten times the lethal dose of the organisms, when in- 

 jected along with them. Here again is presented the remark- 

 able potency of the antagonising substances in the serum, 

 which in this case lead to the destruction of the corresponding 

 microbe. 



The anti-streptococcic serum of Marmorek may be briefly described, as 



