292 FOODS AND FEEDING. XIII. 



assuming that every 1 per cent, of nitrogen corresponds to 

 6'25 per cent: of protein (v. Chap. XI.). 



In grasses, hay, &c., a large proportion of the total nitrogen 

 exists as amides, of which asparagine, CONH. 2 .C.^H 3 (NH. 2 ). 

 COOH (v. p. 217), may be taken as a type. 



Amides are usually stated as being used in the body simply 

 as heat producers and to be incapable of acting like albu- 

 minoids as flesh formers. Though undoubtedly inferior to 

 albuminoids, it appears from recent experiments that amides 

 do to a certain extent perform the functions of these substances. 

 They certainly lessen the consumption of albuminoids and 

 greatly diminish the waste of nitrogenous tissue when albu- 

 minoids are fe$ in insufficient quantity." It is therefore not 

 quite satisfactory to disregard the amides of a food, nor even 

 to merely assign to them, as is often done, the functions of 

 heat producers only. From this last aspect asparagine has 

 only about half the value of starch, when due allowance is 

 made for the nitrogen excreted as urea. 



In other foods, especially in mangolds, a large proportion of 

 the nitrogen exists as nitrates,! and thus probably is devoid 

 of all feeding properties. In calculating the nutritive ratio of 

 a food, therefore, wherever possible the amount of digestible 

 albuminoids should be used and the amides considered as non- 

 albuminoids and equal to about half their weight of starch. 



When this is done it is probable that the calculated "albu- 

 minoid ratio" is wider than it should be, especially in cases 

 where much amide is present, e.g., in silage. 



The " albuminoid ratio" is obviously not a very constant or 

 reliable number, since it depends not only upon composition 

 but also upon digestibility. Still, it affords a valuable means 

 of classifying rations and has proved of much service in feed- 

 ing practice. 



Calorific Value of Food Stuffs. The relative values of 

 food stuffs can, to some extent, be assessed from their power 



* Brutskus, Exper. Stat Record 1899, 275 ; Jour. Chem. Hoc. 1900, abst. ii. 237. 



t This was striking! y demonstrated by an observation made by the author in 1900 

 that some pulped mangold kept for some weeks in a stoppered bottle evolved nitric 

 oxide, doubtless as the result of the action of some denitrifying organism upon the 

 nitrates. A similar production of nitric oxide has been noticed from the pulp of the 

 .sugar beet. 



