DIGESTIBILITY OF FOODS. 99 



has been shown that both in the case of the soluble carbo- 

 hydrates, and of the fibre, the portion digested has always 

 the general formula of starch or cellulose, C 6 H 10 5 , while 

 the portion left undigested is much richer in carbon. 

 It appears, therefore, that while cellulose is digested 

 to a considerable extent, the lignin which is deposited 

 on the tissues as the plant increases in age, and which 

 contains a larger proportion of carbon, is much less 

 digestible. Chemical analysis shows that the fibre of 

 leguminous hay and straw is richer in carbon, and conse- 

 quently in lignin, than the fibre of grass hay or cereal 

 straw. 



The concentrated foods placed in the lower section of 

 the table are seen to be far more thoroughly digested than 

 is the case with hay or straw. When of good quality, 80 

 to 90 per cent, of the organic matter of these foods will 

 be assimilated by the animal, except in those cases where 

 much fibre is present. The albuminoids and fat in these 

 foods have especially a greater digestibility than the same 

 ingredients in hay and straw. The amount of fibre is 

 usually too small for its digestibility to be determined 

 with certainty. The hard fibre forming the husk of seeds 

 is apparently but little digested. The oats employed were 

 of somewhat inferior quality. 



Eoots and potatos are not mentioned in the table; 

 they are apparently very thoroughly digested. 



2. Experiments with Horses. In experiments con- 

 ducted by Wolff the digestive powers of the horse and 

 sheep have been accurately compared, the same food 

 having been supplied to each animal. 



