860 EXPERIMENT STATION RECOBD. 



and ferments (whose presence is not firmly established) which act upon sub- 

 stances not known to occur in the processes of digestion. 



" In milk, the content of ferments which are similar to those which occur in 

 the blood is found to be increased in quantity at periods when the mammary 

 gland is not in a condition of good working activity; such as at the beginning 

 and end of lactation, in mastitis, and in the case of poorly acting glands. 



"It is . . . universally conceded that milk from a gland in these conditions 

 contains exudate from the blood ; the healthier the gland the less the exudate. 

 It follows, therefore, that the traces of such ferments as are found in the milk 

 under normal conditions, are present because they have passed out from the 

 blood either by filtration or exudation. A precisely similar explanation holds 

 good for the presence in milk of substances concerned in the production of 

 immunity. . . . 



" The value of these materials to the infant evidently depends upon the de- 

 gree of absorption which takes place from its alimentary canal. ... It ap- 

 pears that absorption of protein and hence of the immune substances which are 

 attached to the protein molecule may take place directly during the first few 

 days of life. This capacity is, however, of very short duration, especially for 

 foreign protein, which must be broken down before it can be absorbed. 



" The oft repeated assertion of the value to the infant of raw cow's milk 

 fades away when the facts are examined, since, in cow's milk it is found that 

 these so-called 'biological substances' are not absorbed in the alimentary 

 canal but are destroyed there, 



" These considerations also explain the results obtained by those who have 

 investigated the comparative nutritive properties of the raw and boiled milk 

 of a foreign species; these results were fully summarized by me in a recent 

 report to the local government board (E. S. R., 30, p. 760), and it was shown 

 that in dealing with the milk of a foreign species, boiled milk gave perhaps 

 slightly better results than raw milk. In dealing with the milk of a foreign 

 species the real question at issue is that of the chemical changes which take 

 place on heating. , . . 



" If the milk of the same species be now considered, a somewhat different 

 aspect is put upon the whole question, because there appears to be some degree 

 of evidence that native protein is absorbed as such, for a longer period than 

 foreign protein. TJje transitory nature of immunity procured by the suckling 

 does not, however, lead to the supposition that this occurs to any extent, and 

 the evidence all goes to show that the amount of protein which is absorbed as 

 such at any time forms only a small part of the total amount present. 



" The question finally resolves itself into the chemical value of the food 

 material, and it is this fact which brings about the difference commonly ob- 

 served between the condition of the average breast-fed baby and the average 

 artificially fed infant. . . . Considering for a moment the almost certain ab- 

 sorption of protein during the first few days of life it would appear to be very 

 important that the organs should receive native protein. Without entering 

 upon the much discussed question of the effect on the infant of the introduction 

 into the blood stream soon after birth of foreign protein, the mere fact that 

 precipitins are formed by the organism upon the introduction of foreign protein 

 for the express purpose of throwing these substances out of action, would of 

 itself seem to indicate that their presence is not desirable. It has been stated 

 that the injection of foreign protein calls forth less resistance in quite young 

 animals than in older ones, but this probably does not mean that such sub- 

 stances are harmless, but that the organs are not yet sufficiently mature to be 

 able to form precipitins. It has been shown by Schlossman and Moro that the 

 proteins of human milk and of human blood are biologically identical, hence 



