438 CHEMICAL DISCOVERY AND INVENTION 



This includes the indol ring : 



CH 



NH 



which is characteristic of several excretory products, and which 

 the animal body does not seem fitted to produce from other 

 materials. This seems to explain why gelatine is of such very 

 inferior value as food, for on hydrolysis gelatine yields neither 

 tyrosine nor tryptophane. 



Those who desire a more extensive review of the advances 

 which have been made in the knowledge of protein food stuffs 

 cannot do better than read in the Transactions of the Chemical 

 Society the report of a lecture given on May 18th last by Dr. F. 

 Gowland Hopkins, F.R.S., entitled " Newer Standpoints in the 

 Study of Nutrition." 



Even at the present early stage of the development of the 

 subject some practical lessons may be learned. Among these it 

 is evident that one kind of protein-containing food cannot be 

 substituted for another indiscriminately. 



To borrow the language of Saint Paul : "all flesh is not the 

 same flesh ; but there is one kind of flesh of men, another flesh 

 of beasts, another of fishes, and another of birds." This is true 

 in strict biochemical sense, and it is no less true that a diet 

 which will maintain one person in health would not be suitable 

 for every individual of the same race. 



Of late years a number of materials under fanciful names 

 have been offered to the public as possessing extraordinary 

 nutritive qualities. The phospho-proteins are specially valuable 

 in promoting the growth of young animals, and as they are 

 present in milk, preparations made from curd have a certain 

 value. 



Yeast from the brewery is another material which is turned 

 to account in the production of food. Dry yeast contains about 

 half its weight of proteins, and without preparation it may be 

 used advantageously as a cattle food. A product made from it 

 by a patented process closely resembles extract of meat, and 

 may be used in a similar way. 



