SO-CALLED 'BIOLOGICAL PROPERTIES' OF MILK 77 



The work of Spolverini (i) and Snyder may also be consulted. 



Experiments undertaken by me for a report to the Local Govern- 

 ment Board failed to show any evidence of the presence of proteo- 

 lytic action in the milk. The milk was collected by a milking tube, 

 and was free from bacteria ; 50 c.c. of milk was incubated for 

 24-26 hours at 37 C. The protein was subsequently precipitated 

 and a portion of the filtrate examined for soluble nitrogen. Controls 

 were also used. In no case was any increase of soluble nitrogen 

 obtained as a result of the incubation. 



In Human Milk. The same remarks as to the presence of 

 bacteria in the milk of cows are applicable here. The earlier 

 observers, Spolverini (i, 2) (1902), Moro (3) (1902), Friedjung and 

 Hecht (1903), stated that proteolytic activities were to be found in 

 human milk. The milk, however, does not appear to have been free 

 from bacteria. 



Zaitschek was unable to detect any proteolytic activity in human 

 milk, as was also Austin, who worked upon the milk of twenty-one 

 women in different states of health. Austin obtained no hydrolysis 

 of protein even after fourteen to sixteen days, and he concludes 

 (i) that there is no evidence of auto-digestion of human milk, at least 

 under the conditions appertaining to such digestion in organ tissues, 

 and (2) that the digestive disturbances of infants fed upon human 

 milk can have no relation to such an enzyme, as the milk of both 

 healthy and sick women was examined. 



Miiller and Jochmann investigated the presence of proteolytic 

 activity in colostrum expressed from the breast both before and after 

 the birth of the child. They used a nutrient medium, consisting of 

 blood, serum, and bouillon, in Petri dishes, the evidence of proteolytic 

 activity being shown by any impairment of surface. These authors 

 found that there was constant evidence of proteolytic activity in 

 the fluid expressed in the last two months of pregnancy and in the 

 early days after birth, but that this subsequently fell very rapidly, 

 being small after the first few days and generally absent by the 

 eleventh day. They believe that this action is due to the colostrum 

 corpuscles. In view of the probability that some of the colostrum 

 corpuscles are leucocytes, there is no difficulty in supposing that this 

 ferment is present in colostrum, since leucocytes are known to show 

 proteolytic activity. 



Grimmer (i) investigated the presence of proteolytic ferments 

 in the resting and active gland of a number of animals. He found 

 that some degree of auto-digestion does take place in the tissue. 

 He does not suggest the possibility of this action being bacterial 

 in nature, and believes that it is present in the cells of the gland. 

 The action was at all times too weak to have any effect upon foreign 

 proteins, and was less marked in the resting gland than in the 

 active gland. He also showed the presence of an ereptase which 

 was capable of splitting polypeptides, with tyrosin as one of the 

 products. 



