120 MILK AND ITS HYGIENIC RELATIONS 



effect. The real interest of their presence lies in the insight 

 thus obtained into the mode of action of the mammary gland. 

 There can be no doubt that these substances are derived from the 

 blood stream and pass out into the milk. 



Greater amounts of these substances are present in colostrum, 

 and the fact that the haemolytic factors are found only during the 

 colostral period, or at such other periods when the gland function 

 is in some degree abnormal, adds weight to this point. 



The Production of Passive Immunity by Suckling. The passage 

 of substances concerned in the production of immunity from the 

 blood to the milk, has been widely studied. For this purpose it 

 has been found easier to immunise the mother, or inject a known 

 antitoxin, whose presence both in the blood and in the milk 

 could be readily detected. In some cases the relative strength 

 of the antitoxin in the blood and in the milk was examined, and 

 also the effect on the milk of raising the antitoxin content of 

 the blood. 



The results obtained have shown conclusively that whatever 

 properties are possessed by the blood of the mother are possessed 

 also by the milk, although to a lesser degree. These properties 

 are known to be attached to the proteins, and there is a good deal 

 of evidence to show that they are destroyed in the alimentary 

 canal when the protein undergoes digestion. 1 



Hence, when the digestive functions of the child are established 

 after birth, the immune properties present in the milk are destroyed, 

 and they then possess only the actual food-value of the protein 

 to which they are attached. 



The possibility of the absorption of protein without digestion 

 in the early days of life has been mentioned in Chapter III, where 

 the identity of the whey-proteins with those of the blood was 

 shown. If this occurs, it would be likely that any immune properties 

 possessed by the mother's blood would be absorbed by the infant 

 directly, until such time as the digestive functions have sufficiently 

 developed to destroy the protein-complex. 



Numerous experiments have been conducted upon these lines, 

 and all show that the above proposition holds good. 



The early experiments were carried out by workers who were 

 investigating the transmission of immunity from the parent to 

 the offspring. Ehrlich found that when a mother was rendered 

 immune to abrin, ricin, robin or tetanus, this immunity was trans- 

 ferred to her young by means of suckling. The immunity thus 

 conferred lasted for about a month. By the third month of life 

 it was much reduced, and shortly afterwards it disappeared entirely. 

 The animals used by him were mice. 



Hamburger (2), working on somewhat similar lines, showed 

 definitely that this immunity was transferred by suckling. He 



1 Cp. Michaelis and Oppenheimer, Pick and Obermeyer, Sacconaghi and 

 Bauer. 



