240 MILK AND ITS HYGIENIC RELATIONS 



remembered that caseinogen has been shown to be a substance 

 apart from the blood-proteins. 1 



As a general conclusion it may be stated that antigens are not 

 affected by just boiling milk, but that some effect is produced when 

 the heating is prolonged. In this connection the observations of 

 Delepine on the temperature reached in the process of drying milk 

 are of considerable interest.* 



On the Presence of further Substances in Milk concerned in 

 the Nutrition of the Organism. The work of several authors 

 indicates that there are in milk several substances which are of 

 great importance for the adequate development of the organism. 

 These investigations have been carried out for the most part upon 

 adult animals which have been deprived of one or other of their 

 normal food-stuffs. The results are somewhat fragmentary from 

 the present point of view, but cannot be entirely omitted. 



The earliest work was that of Stepp, who fed mice upon food 

 which had been previously treated with alcohol and ether to remove 

 the lipoids. He found that mice fed upon this food as the sole 

 diet did not survive very long. If, however, a small quantity of 

 milk was added to the dietary no detrimental effect was observed. 

 The minimum amount of milk was given which was able to keep the 

 animals ah' ve. Stepp found that rather more boiled milk had to be 

 given than raw milk in order to ensure the survival of the animals. 



The work of Hopkins upon rats showed that where an insufficient 

 dietary was given, the addition of minute quantities of milk caused 

 a most striking difference in the rate of growth of the animals. 

 No work was carried out with heated milk, so that these experiments 

 are somewhat outside the scope of the present chapter. 



Funk (i, 2, 4) in his investigations upon the deficiency diseases 

 believed that he had obtained evidence of the presence of a non- 

 phosphorus-containing compound which was necessary for the life of 

 the animal. This substance was termed by him vitamine, and was 

 isolated by him from samples of dried milk. Funk (3) alleged that 

 this substance was destroyed by boiling, but the evidence in support 

 of this statement is indefinite and cannot be regarded as conclusive. 

 Moreover, the substance prepared by Funk is now very generally 

 believed to be a mixture of several substances, so that much stress 

 cannot at the present time be laid upon this work. There seems 

 little doubt that milk does contain substances of (at present) unknown 

 composition which are essential for the life of the animal where 

 milk is the sole dietary, but there is no evidence to show that 

 these substances are destroyed by boiling, especially when the 

 heat is not applied for prolonged periods and when a temperature 

 not exceeding boiling-point is used. The work of Stepp suggests 

 that there may be some loss of ' vitamine ' as a result of boiling 

 milk. This loss, however, if it occurs, is evidently not sufficient 

 to affect the nutritive value of milk for infants, as has been 

 abundantly shown in the preceding chapters. 



1 Cp. Chap. III. 8 Cp. Appendix F. 



