EXPERIMENTAL DATA OF RAW AND BOILED MILK 177 



467 guinea-pigs were fed from birth onwards on various forms of 

 cows' milk, and 156 were left with their mother and thus received 

 their natural food. Guinea-pigs were selected for the purpose of 

 experiment as being to some degree analogous with calves, that 

 is to say, both species are herbivorous, and in both cases the young 

 are dependent for a comparatively short period upon their mother's 

 milk as sole food. 



The guinea-pigs were not fed exclusively on milk but were 

 allowed other forms of food, the nature of which is not specified. 



As the litters of young pigs were born they were separated 

 into various groups, being divided equally as far as possible. No 

 weakly ones were placed in the groups used for artificial feeding, 

 these being all left with their mothers and forming part of the 

 series of pigs dealt with for the natural-feeding controls. The 

 guinea-pigs on artificial food were divided into three groups : 

 (a) Those fed on raw milk, (b) on pasteurised milk (heated to 140 F. 

 for twenty minutes and then rapidly cooled), and (c) on boiled milk. 

 (The boiled milk was slowly heated to boiling-point, kept at that 

 temperature for one minute and then rapidly cooled.) A special 

 apparatus was devised by which I c.c. of milk was fed to each 

 guinea-pig five times a day. After the twentieth day milk was 

 accessible to the pigs for ten days longer, after which it was 

 withdrawn from their diet. The milk used for the purpose was 

 of the best quality, obtained from the experiment station and 

 from tuberculin-tested cows, and in no case was it more than eight 

 hours old when fed to the pigs. 



The effect of feeding with the three kinds of milk was measured 

 (a) by the mortality among the experimental animals and (b) by 

 the average weight at different periods of the surviving animals. 

 Schroeder gives the following table : 



Percentage Mortality among the Guinea-pigs 



Schroeder emphasises the great superiority of mother's milk 

 over that of any form of cows' milk for the young guinea-pigs, 

 more especially as the weakly ones were always left with their 

 mothers. This last fact accentuates the marked difference between 

 the two groups. As regards the artificially fed groups he points 



