BIOCHEMISTRY 31 



BIOCHEMISTRY. By J. C. Drummond. D.Sc, F.I.C. University 

 College, London. 



AIilk.--Fe\Y problems in biochemistry have attracted more 

 attention recently than certain aspects of the physiological 

 process of milk secretion, and many papers in the last year have 

 dealt with the influence of the diet of the lactating animal on 

 the composition and nutritive value of the milk. 



The importance of a well-balanced ration adequate in 

 vitamins to ensure the production of a milk rich in these indis- 

 pensable factors has been recognised in a general way since the 

 experiments of McCollum, Simmonds and Pitz (/. Biol. Chem., 

 1 91 6, 27, 33), and McCollum and Simmonds {Amer. J. Physiol., 

 191 8, 46, 275), but nevertheless the recent results of Dutcher, 

 Eckles, Dahle, Mead and Schaefer (/. Biol. Chem., 1920, 45, 1 19) 

 and of Hess, Unger and Supplee (/. Biol. Chem., 1920, 45, 229) 

 are interesting. These two groups of investigators showed 

 almost simultaneously that cows fed on rations low in the 

 antiscorbutic factor yield a milk which is deficient in this 

 substance. 



More recently this influence of this accessory factor content 

 of the diet on the nutritive value of the milk has been further 

 emphasised in the case of the other two vitamins, namely A 

 and B. Drummond, Coward and Watson {Biochem. J., 1921, 

 15, $40) found wide variations in the vitamin A content of milk 

 fats and butter which appeared to be due largely to differences 

 in the rations of the cows, an observation which has recently 

 been confirmed for the A factor and extended to apply to the 

 B factor by Kennedy and Dutcher in America (/. Biol. Chem., 

 1922,50,339). 



The significance of these discoveries is far-reaching, for it is 

 at once apparent that sooner or later the regulations concerning 

 the control of the composition of milk and milk products must 

 be reconsidered from this standpoint. 



A series of papers by Hartwell raise a number of interesting 

 problems. In a study of the influence of diet on mammary 

 secretion in rats {Biochem. J., 1 921, 15, 140) she found that, 

 whilst an excess of carbohydrate in the diet had practically no 

 effect on the milk supply and excess of fat relatively little, an 

 excess of protein appears to alter the composition of the milk 

 and after a time the milk supply ceases. Following up this 

 observation she recorded {Biochem. J., 1 921, 15, 563) a confirma- 

 tion of this detrimental effect on the young of a high protein 

 diet (40 per cent, by dried weight) for the mother during lacta- 

 tion. The cause of failure of the young is, in her opinion, due 

 to an actual toxicity of the milk as well as to the failure of the 

 milk flow. She does not regard the symptoms as being due to 

 absence of vitamins, for she records cases in which healthy litters 



