550 



PHYSIOLOGY AT THE FARM. 



ent stages of life and condition. The weights in pounds de- 

 note per cent in carcass. 



But short-horn steers of four years old have attained the 

 great weight of 2100 Ib. 



When the constituents of a particular kind of food, or of a 

 particular diet, are not known according to the exact percent- 

 age of flesh-formers and of heat and fat giving principles, but 

 are more rudely divided into nitrogenous and non-nitrogenous 

 principles, some care is required in estimating the actual 

 amount of nourishment received. With respect to the nitro- 

 genous products of vegetables, it must be ascertained whether 

 or not all of those present are really digestible and nutritious, 

 and not injurious ; and as to the non-nitrogenous, it must be 

 considered whether cellulose or woody fibre does not form any 

 important proportion of the mass. When cellulose, called also 

 celluline or woody fibre, is in its most tender and most deli- 

 cate state, as in many common food-stuffs, it is now known to 

 be sufficiently digestible, and stands probably, as a nutritive 

 substance, on the same footing as starch and sugar ; but when 

 it belongs to a more advanced state of the vegetative process it 

 is utterly indigestible, and is passed by the animal from the 

 bowels unchanged along with the excrement. It appears, 

 moreover, that the pectine compounds have a less feeding 

 value than starch or sugar. On the contrary, according to the 

 conclusions of Lawes and Gilbert, a given amount of fatty 

 matter in food may be considered as equivalent to about 2J 



