THE FOODS FED TO BEASTS 185 



nitrogen multiplied by 6 J is a good enough approximation, but 

 in some of the less concentrated foods, like hay and turnips, 

 it has been found in practice that some further information 

 is desirable. For this reason the nitrogenous matter is 

 commonly divided into the two groups of the " true albumi- 

 noids " and the "amides" (see p. 147). The particular 

 amino acids required by the beasts will vary according to 

 the needs of the animal, which will depend partly upon the 

 species, partly upon the age, and partly upon the condition 

 of health. Foods may not infrequently contain a few special 

 nitrogenous matters, such as some of the nitrogenous gluco- 

 sides. Some of these, of which amygdalin and linimarin 

 may be taken as types, evolve prussic acid under certain con- 

 ditions (see p. 137). Potatoes contain another special nitro- 

 genous glucoside called solanin. Potato eyes may contain 

 large quantities, even up to 5 per cent., but the haulms do 

 not usually contain more than about 0*03 per cent. This 

 substance is slightly poisonous, but the amount present is 

 usually too small to produce any serious effect. Special 

 foods may sometimes contain nitrates, especially crops grown 

 under droughty conditions. Probably the nitrates them- 

 selves are not very harmful, but they usually accompany other 

 forms of nitrogen, neither protein nor amide, and injurious 

 results have been observed under these conditions. Man- 

 golds, for example, are not satisfactory to feed immediately 

 after pulling, but after an interval of storage they become 

 riper, the nitrates, among other changes, being converted 

 into organic nitrogen bodies, and the irritating compounds 

 being built up into proteins. In India, juari and other 

 fodders when cut unripe in droughts act in a similar 

 manner. In sound food the nitrogen in the forms of true 

 albuminoids and amides (see p. 181) usually adds up to the 

 total nitrogen, but in unripe root crops and leaves there 

 are often other forms of nitrogen than these. A portion 

 of the other forms will often be nitrates, but there are other 

 nitrogenous compounds whose constitution is little under- 

 stood. For a large number of purposes no effort is made to 

 do more than determine the total nitrogen in the foodstuffs. 



