MANURING FOR MEAT 181 



acids and some di-amino. Some of them are straight, and 

 some of them are branched. An important cyclic compound 

 is indole, which the animal body does not seem capable of 

 synthesizing. A common hydrolytic product of the break- 

 down of some proteins is tryptophane, which contains the 

 indole ring. The proper utilization of the proteins absorbed 

 from the food appears to depend upon minute traces of 

 substances which are known as food hormones. little is 

 known about the exact character of these bodies, although 

 some are compounds of pyridine. When tryptophane is 

 broken up in the animal body, it is probably excreted as 

 skatole, which is of a purgative character. One of the 

 results of feeding excessive quantities of protein material 

 is usually to produce a loosening effect. This is probably, 

 at least in part, due to the excretion of superfluous quantities 

 of bodies like skatole. Frequent mistakes in feeding cattle 

 have been made by the use of excessive quantities of nitro- 

 genous food, but it is not always practical to get, on 

 economic lines, the exact mixture one requires. Maize which 

 contains no tryptophane is known to be somewhat binding 

 and heating in its effects. The simple amino acids, like 

 aspartic and glutaminic acids, are produced by the hydrolysis 

 of proteins in such large amount that relatively they are 

 not urgently needed. Even the benzene nucleus seems to be 

 f airly easily obtainable either synthetically or analytically. 

 The substances constituting the nucleus of most cells 

 contains some of the purine bases, which give rise to uric 

 acid in man, but to allantoin in beasts. There does not, 

 therefore, seem to be the same risk of over supply of purine 

 bases to animals that there is to man. In estimating the 

 feeding value of foodstuffs, it is not uncommon to differentiate 

 between the true albuminoids and the amides, that is to 

 say, between nitrogen precipitated by lead acetate and 

 ammonia volatile with caustic alkali and steam, or some such 

 similar division. Such bodies as asparagine will only yield 

 half their nitrogen by distillation with caustic alkali and 

 steam. Such a division, at the best, does not really answer 

 the question we wish to ask. What we really want to know 



