114 THE CHEMISTRY OF THE FARM 



might be met by supplies of carbohydrates and of fat. 

 This is to a great extent true ; but a diet very poor 

 in albuminoids is not found to be consistent with 

 real bodily vigour. 



The ash constitue^its present in the food are the 

 same as those found in the animal body ; all that is 

 accomplished by the animal is to select from the 

 digested ash constituents those of which it is in want. 



•(2) Digestion. — The object of digestion is to bring 

 the solid constituents of the food into a form suitable 

 for absorption into the blood. The work of digestion 

 is partly mechanical and partly chemical. The food is 

 reduced to a soft pulp by mechanical force and driven 

 through the alimentary canal. The solution of the 

 food is accomplished by means of certain enzymes 

 (hydrolysing agents) supplied by the secretions of 

 the canal. 



Of the carbohydrates of the food some, as fruit 

 sugar, are already soluble and diffusible, and need no 

 digestion ; others, as starch and cellulose, are naturally 

 insoluble. The digestion of carbohydrates commences 

 with the action of the saliva, which has the property 

 of converting starch into sugar (maltose). This action, 

 in the case of ruminants, is prolonged by the tem- 

 porary sojourn of the food in the paunch and its 

 return to the mouth in chewing the cud. The diges- 

 tion of the cellulose by a fermentative process com- 

 mences in the paunch.^ The further solution of 



• None of the secretions of the alimentary canal are capable of 

 digesting cellulose ; but, according to Horace Brown, oats and other 

 seeds contain an enzyme capable of dissolving cellulose ; this enzyme 

 is especially developed during germination. To what extent such an 

 enzyme is generally present in vegetable food is as yet unknown, 



