434 PHYSIOLOGY OP THE DOMESTIC ANIMALS. 



First. Vegetable fibre is capable of being digested to a more or 

 less degree by all lierbivora and even to a certain extent by the hog, the 

 co-efficient of digestion lying, in green and dry fodders, between 45 and 75 

 per cent. In vegetable foods, such as grains, roots, and bulbs, and the 

 artificial nutritive substances made from such materials, all of which are 

 rich in cellulose, the digestibility becomes greatly reduced, and, in fact 

 many such products may be said to be entirely undigestible. It is prob- 

 able, again, as already mentioned, that a certain amount of cellulose 

 which disappears in its passage through the intestinal canal may be ex- 

 plained as due to the development of carburetted hydrogen and carbon 

 dioxide and other fermentations. 



Second. The non-nitrogenous extractive matters, as found in beets 

 and potatoes and seeds, are almost completely digested,- only about 

 2 per cent, escaping the action of the digestive fluids, though in green 

 fodders the digestive co-efficient of these materials may sink from 84 to 

 48 per cent. In this connection the remarkable fact appears that the 

 amount of soluble non-nitrogenous food-constituents which undergoes 

 digestion, together with the amount of cellulose which is digested, almost 

 exactly equal the total sum of non-nitrogenous extractive matters found 

 in the food, and in this we have, therefore, a means of estimating the 

 quantity of non-nitrogenous extractive matters actually digested and 

 absorbed. The digestible portion of the non-nitrogenous extractive 

 matters in any food may be estimated in nutritive value as pure carbo- 

 hydrate, and therefore compared with starch. 



Third. As regards fat, it may be stated that, when perfectly pure, 

 fat is entirely digested, but since fat in the ordinary foods is not pure 

 and contains other indigestible constituents, it is evident that the digest- 

 ive co-efficient of fat will be subject to great variation. In clover and 

 various oil-cakes this co-efficient varies between 80 and 90 per cent.; in 

 seeds, between fiO and 90 per cent. In beets and potatoes fat may he 

 regarded as entirely digested, while, on the other hand, the fat in green 

 foods, although present in smaller amount, still varies in digestibility 

 through very wide limits. Thus, 80 per cent, may be absorbed, or only 

 20 per cent. In general, in this connection, clover is more readily 

 digested than grasses, while straw of the hulled fruits is more digestible 

 than the straw of the hulled cereals. 



Fourth. The nitrogenous constituents of the food are generally 

 regarded as albumen, although, of course, other nitrogenous materials 

 are often constituents of foods. In beets and potatoes albuminous 

 matters are, as a rule, entirely digested, in seeds a certain amount 

 escapes, the co-efficient of digestion varying from 60 to 90 per cent. In 

 green and dried fodder great variation is met with, the co-efficient of 

 absorption varying between 17 to 75 per cent., as a rule, the digestibility 



