SUMMARY OF CHAPTER V 



THE SO-CALLED ' BIOLOGICAL PROPERTIES ' OF MILK 



A. THE FERMENTS OR ENZYMES 



A GREAT deal has been written and spoken about the ferments 

 or enzymes in milk, and many writers have attributed great 

 importance to the presence of these substances. It will be of 

 interest to consider briefly how the discussion upon this question 

 has arisen. 



Before the beginning of the present century physicians do not 

 appear to have taken much interest in the question, although a 

 considerable amount of work had already been done by numerous 

 chemists. In the year 1900, Professor Escherich, of Vienna, at 

 that time one of the foremost physicians for children's diseases, 

 sought to account for the difference in progress made by infants 

 fed on boiled cows' milk as compared with breast-fed babies, by 

 suggesting that milk contained certain ' properties ' which were 

 destroyed by boiling and which might be of value for the infant. 

 It may be remarked here, that boiled milk is almost universally used 

 on the Continent, since raw milk, even though carefully collected, 

 is not considered a safe food for infants. This idea, once started, 

 opened up a very wide field of investigation and occupied the 

 attention of a number of observers for many years. Recently, 

 the literature on the medical side has decreased in amount, and 

 the interest appears to have slackened considerably. The investiga- 

 tions are, however, still continued by dairymen for purposes which 

 are not directly connected with the feeding of infants, and which 

 will be alluded to briefly in this chapter. 



The discovery in milk of a considerable number of ferments 

 has led a number of people to describe milk as a ' living substance,' 

 and to credit milk with powers which investigation has not sub- 

 stantiated. Before dealing in detail with the ferments which are 

 found in milk, a few preliminary considerations are necessary. 



It must be remembered that milk is a secretion produced by the 

 mammary gland, and its production is on analogous lines with the 

 secretion of saliva by the salivary glands. The knowledge which we 

 possess of secretory processes in general shows that although each 



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