SOME ASPECTS OF THE IMMUNITY QUESTION. 243 



and by the commencement of the third month has disap- 

 peared, the protective substance no longer exists in the 

 organism, and obviously this has been derived from anti- 

 bodies of the mother. By pairing the offspring of parents 

 which were resistant to abrin the succeeding - generation 

 was found to be as susceptible as normal animals, and 

 therefore the ovum possesses no idioplasm capable of effect- 

 ing a true heredity of the acquired immune condition. 

 Apparently fcetal immunity is an accepted fact for 

 certain diseases and certain animals ; but though this may 

 play some part, Ehrlich's further observations showed that 

 the protective, or anti-bodies, which are concerned in con- 

 ferring immunity, are transferred by the milk. The passage 

 into milk of drugs, such as iron (42), iodide of potassium, 

 or garlic, is well established, and further, this fluid may 

 not only contain micro-organisms which are pathogenic 1 or 

 harmless (43), but, as Ketscher (44) has shown, goats pro- 

 tected against cholera yield milk which behaves like the 

 serum of immune animals, since this fluid can render 

 guinea-pigs refractary to a lethal injection of cholera 

 bacteria, and this protective power was exerted when the 

 protective material and cholera poison were introduced 

 into different parts of the body ; lastly, if the intoxication of 

 cholera is already produced the milk possesses the power 

 of abolishing this and curing the disease. 



This important discovery of lactation immunity was 

 conclusively proved by the susceptibility shown by the 

 offspring of highly immune mothers which were suckled by 

 a normal nurse and the immunity which followed when, 

 conversely, offspring of susceptible mothers were suckled by 

 an immune nurse. The degree of immunity also, as might 

 be expected, since there is a transference of anti-bodies 

 present in the milk, augments with the duration of lactation. 



1 The following observation is of interest. Nocard has shown that 

 suckling goats easily succumb when anthrax bacilli are injected into the 

 mamma by way of the lactiferous ducts. A goat rendered immune is un- 

 harmed by this proceeding, although the bacilli live within the gland for an 

 indefinite period, and the milk is shown to possess virulent properties, since 

 sheep inoculated with such milk die of typical anthrax. 



