to the Rearing awl Feeding of Catlle. 
229 
blood is afterwards converted into flesh. In order to show that the 
transformation is actually effected without change, we ref(!r you 
to the composition of albumen, blood, and flesh, as ascertained by 
the accurate analyses of different chemists : — 
Vegetable Albumen. Ox ISlood. Flcsli. 
Scliercv. Mulder. l'layf:iir, lioeckmaii. Pkiyfair. Boifckman. 
Cmbon . 55- 100 rvl-99 5J-3.5 51-3G 54-13 54-18 
Hydrogen 7-055 6- S7 7-50 7-G7 7.89 7-93 
Niliogfii 15-9fiC 15-G« 15-7(i 15-77 15.67 15-71 
Oxygfii. '21-819 22- J8 22-39 22-20 22-32 22-18 
Now, as flesh can only be formed from substances of its own 
composition, the value of different kinds of food vi'ill vary accord- 
ing to the quantity of albumen contained in it. Boussingault 
many years since endeavoured to lay dow n the principle that the 
value of a particular kind of food depended upon its proportion of 
nitrogen.* This principle was rather arbitrary ; because, although 
it may be true enough as far as regards flesh, it is quite erro- 
neous as regards the production of tallow or the support of respi- 
ration. Boussingault's generalization arose from an ignorance of 
the functions of the constituents of food destitute of nitrogen. 
Farmers have always been very anxious to obtain a correct list of 
the equivalent values of various kinds of food, but have never yet 
succeeded. Mr. Rham has compiled a listf from the experi- 
ments of the most distinguished agriculturists; but it is impossible 
to rely upon equivalents obtained by mere experiment. The 
reason for this assertion will be obvious, when it is considered that 
the quantity of food necessary to keep an animal in a certain state 
must vary according to the conditions in which it is placed, i. e., 
according to the temperature to which it is exposed, and to the 
amount of exercise which it receives. In a hot day it will require 
much less food than in a cold. Equivalents of food may be cor- 
rect, as far as the same animal is concerned, when it is placed in 
the same conditions ; but they can be of little value as regards 
other animals, because, as we shall afterwards show, the size of 
the lungs of an animal occasions a great difference in the amount 
of food consumed. 
It is very important for us to know how much water each kind 
of food contains. Thus in giving a pig 100 lbs. of potatoes, we 
actually give it only 28 lbs., because 72 lbs. of this food consist of 
water. The following table, drawn up from analyses made by 
myself, exhibits the amount of diy organic matter contained in the 
most usual kinds of food: J — 
* Annales de Chimie et de Physique, Ixiii., 225. 
f Journal R. E. Agric. Soc, vol. iii. p. 79. 
X The analyses of swedes, turnips, maiigold-wurzel, potatoes, and car- 
lots are made upon samples procured from the field, and not upon stored 
