EXPERIMENTAL DATA OF RAW AND BOILED MILK 173 



time, taken altogether, they may suffice to show sufficiently well 

 the general nutritive value, and to serve as supporting evidence 

 when taken in conjunction with clinical data. 



Of recent years experimentation on animals has practically 

 ceased, but it is of interest to consider such work as has been accom- 

 plished before proceeding with the clinical data. 



One advantage is undoubtedly presented by animal experi- 

 mentation in connection with the present problem. Clinicians are 

 very frequently predisposed in favour of raw or of boiled milk for 

 their patients. In these circumstances they hesitate to employ 

 any other variety of milk, since they only desire to utilise what 

 they believe to be the best form of nourishment. In animal experi- 

 mentation, however, it is possible to feed groups of animals over 

 the same period upon both raw and boiled milk, and to compare the 

 results obtained either with one another or with the results obtained 

 by breast-feeding alone. Hence in the animal experiments it is usual 

 to find the experiments carried out in two or three series worked 

 simultaneously, whereas in the clinical work this is not the case. 



Experiments upon Guinea-pigs. In spite of the difficulties 

 considered above in regard to the feeding of guinea-pigs with milk, 

 a considerable number of experiments have been carried out. 

 These experiments have added to our knowledge of desirable 

 foods for guinea-pigs, and have incidentally offered some evidence 

 in regard to utilisation of cows' milk for infants. There seems 

 little doubt, however, that guinea-pigs cannot live on a milk diet 

 only, the addition of vegetable substances being necessary. Only 

 one observer has stated that he was able to keep guinea-pigs alive 

 on milk alone, and his investigations have not been confirmed, 

 nor have satisfactory data upon the subject been published. 



The most conclusive experiments have demonstrated the 

 importance of breast-milk, even in the case of young guinea-pigs, 

 who cannot live on milk only. 



As regards the use of raw or boiled cows' milk, no marked differ- 

 ence in the nutritive value could be detected. As a whole, however, 

 the boiled milk appeared to have given more favourable results 

 than the raw milk. 



Experiments on Rats and Mice. Experiments were conducted 

 by Keller on mice fed upon raw milk and upon boiled milk. Keller 

 was unable to detect any difference in the nutritional condition of 

 the sets of animals. 



Experiments were carried out by myself on rats, the animals 

 being fed upon raw and boiled milk of the finest quality ; an 

 additional series of rats were fed upon dried milk. These investi- 

 gations are open to the objections which have already been pointed 

 out generally in regard to animal experimentation. With this 

 reservation, no difference could be detected between the raw and 

 the boiled milk series, although some slight advantage appeared 

 in those fed on dried milk. 



