Dlli'J-ETlC DEFICIENCY. 



Bv Hi-:nk\' Hamilton (iKKK.x. 15. Sc. F.C.S. 



The i)uri)oso of the present paper may at the outset he rout:^hl_\- 

 stated to he a hrief resume of certain recent work n]>on feeding 

 prohlems, and the significance of certain constituents of feeding- 

 stuffs for the maintenance of hfe and health. 



By way of introduction, it may he recalled that, until within 

 comparatively recent \'ears, the classification of the earlier physio- 

 logists, resulting in a difterentiation of foods according to the 

 proportion of proteins, carhohydrates, fats, and minerals which 

 they contained, was regarded as fairly adequately representing 

 all the constituents which had to be taken into account in consi- 

 dering the nutritive value of a diet. 



A sharp distinction was of course drawn between the diges- 

 tible and indigestible moiety of each constituent, and a great 

 deal of classical work had alreadv been done upon the digestibi- 

 Ht\- of the various components occurring in dift'erent natural 

 foods as fed to man and to live stock. 



Long before the end of the last century, the compilation of 

 tables showing the digestive coelticients and ntttritive vahie of 

 such food-stuff's was well advanced. A clear distinction was 

 drawn between the metabolism of proteins, fats, carbohydrates, 

 and minerals, and the broad functions of each in the aniiual 

 economy was understood, although at the same time the distinc- 

 tion between different forms of these basal constittients was little 

 more than recognised. The physiological sigr.'iicance, for ex- 

 am])le, of difference in kind of protein, was largely a matter of 

 conjecture, and it was customary to measure the protein value of 

 a food by its total nitrogen content, and to measure ]>rotein meta- 

 bolism in the body by the excretion of total nitrogen in the urine. 

 Definite relationships between the calorific value and intermeta- 

 bolic e(|tiivalents of proteins, fats, and carbohydrates, were 

 established, and feeding standards laid down for different classes 

 of animals tinder varying conditions, due respect being paid to 

 energy requirements and to the quota of protein necessary for the 

 repair of waste tissue. 



Concerning the more intimate processes of the living 

 organism in relation to the destiny of ingested food, little was 

 known. As Cathcart* ptits it : — 



Carl \'oit, even in 1902, after forty years of sirenuous work, could 

 say no more than that "' the unknown causes of metabolism are found 

 in the cells of the organism. TItc mass of these cells and their power 

 to decompose materials determine the metabolism." 



We are still in much the same position to-day, but yet the 

 beginning of the present century may be regarded as bringing 

 with it several strikingly new developments in the luore detailed 



*" Physiology of Protein Metabolism" (1912). 

 A 



