THE PLACE OF PROTEIN IN NUTRITION. 35;^ 



It is impossible, as yet, to outline in detail final plans for 

 feeding- experiments with the natural mixtures of amino-acids 

 as they occur in ordinary feeding-stuffs in order to demonstrate 

 the relative efficiency of the amino-acids for maintenance and 

 growth until further data have been secured from the researches 

 of the first two divisions. In such experiments the necessity 

 for exactly controlled conditions is obvious, and cannot be over 

 emphasized. Recent ex])eriments indicate clearly that in re- 

 stricted but natural rations certain accessory compounds which 

 the animal organism cannot synthesise may be absent, or in 

 some cases it is possible that toxic materials may be present 

 to exert a slow but detrimental eft'ect. Further, it has been 

 showai in the case of swine that unknown If actors operative in 

 the normal environment of this species, such as soil-rooting and 

 natural water, are r)f considerable importance, and may aft'ect 

 its nutrition. The importance of the mineral side of a ration 

 has also been well estal)lished. Fiu'ther, the researches of the 

 last few years have clearly demonstrated that nutrition experi- 

 ments of short duration, even when accompanied by elaborate 

 chemical and physiological analysis and examinations, gi\e but 

 little, if any, insight into the value of a feed for long-continued, 

 •normal and healtjiy growth. 



In view of these considerations it would seem that the first 

 tiling to Ije accomplished is to select some one standard ration, 

 and demonstrate beyond a doubt that this ration under exactly 

 controlled conditions will produce normal growth for a long 

 time, say, six to teai months. 



It is not my intention to suggest detailed plans for such 

 an experiment. Init if the above conditions can be obtained, we 

 shall have an excellent standard ui)on which to base future work. 

 Further, direct experimental evidence will be obtained that this 

 ration contains all the necessary food nutrients, and all the 

 essential com])oimds like vitamines. lipoids, etc., retjuired for 

 the maintenance, the growth, and the fattening of the particular 

 animals used ; also, that this ration does not contain toxic 

 materials that exert a detrimental influence on growth. 



Such studies mark the beginning elf a new era in the chemis- 

 try and i)hysiolog'y of nutrition. Our rapidly increasing evi- 

 dence on the nutritive fimctions of the amino-acids will no dottbt 

 be helpful in the interpretation of past and future feeding ex- 

 periments. Is it not possible that in the near futtu-e we shall 

 calculate balanced rations from their amino-acid content that 

 will be most efficient for maintenance, growth, and fattening of 

 farm animals? Undoubtedly the practical and economic impor- 

 tance of modern nutrition investigations will be aj^preciated by 

 the general public oidy when the findings make possible a better 

 economic and nutritive valuation of feeding-stuft"s. An eminent 

 authority has said: " It is perhaps not too Utopian to expect that 

 the day mav arrive when amino-acid concentrates may serve to 

 render perfect the mixture of proteins in a fodder like maize." 



( Read. Jiilx T, igi7.) 



