a, 
186 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
wholly upon the vegetable world, either directly, as do the herbivora, 
or indirectly, like the carnivora. ‘ 
If now we consider the function of food, we shall see that it is four- 
fold in the young animal, viz., to supply the means of growth, to repair 
waste tissue, to maintain animal heat, and to supply muscular force; 
while in the adult animal the last three functions exist. 
The tissue of the animal is mainly bone and muscle. The bone is 
composed almost entirely of phosphate of lime and a compound rich in 
nitrogen. The muscle is composed mainly of fibrin, which is also a ni- 
trogenous compound, that is, an organic compound containing nitrogen, 
resembling in composition vegetable albumen. 
Fat, on the other hand, is a compound which contains no nitrogen, 
but is composed of carbon, hydrogen, and oxygen. t 
Since, then, the animal is unable to elaborate for itself these compounds, 
it is obvious that to provide for the growth and development of bone 
and muscle there is need that a portion of the food should consist of 
such vegetables as may be able to furnish these nitrogenous compounds. 
Furthermore, since, like any other machine, there is constantly going 
on a certain amount of “wear and tear,” so to speak, of the machine, 
there is needed, even in the adult animal, a certain amount of these 
same nitrogenous compounds to repair this continual waste of tissue. 
When we come, however, to consider the other functions of food, viz., 
.the maintenance of animal heat and the supplying of muscular force, 
if has, during the past few years, been pretty conclusively established 
that these functions may be performed quite as effectively by non-nitro- 
genons food, as for example starch, fat, and sugar, compounds composed 
only of carbon, hydrogen, and oxygen, as by nitrogenous food. 
Im the production of fat also, since this is a compound containing no 
niirogen, it is elaborated from non-nitrogenous food, but nevertheless 
its ready production appears to be dependent upon the presence to a 
certain extent of nitrogenous fcod in the diet. 
By reference now tothe several analyses given of grasses and cereals, 
he following constituents are given in their composition: Oil, wax, su- 
gar, gum, dextrin, starch, soluble starch, amylaceous cellulose, alka- 
line extract, and cellulose. The above-mentioned compounds are com- 
posed wholly of carbon, hydrogen, and oxygen. There are given also 
the following: Albumen soluble, albumen insoluble, and zein. These 
three last mentioned are compounds rich in nitrogen, but containing also 
earbon, hydrogen, and oxygen. 
It remains yet to consider the relative nutritive value of these several 
compounds. There exists a strong analogy between the vegetable and 
animal in this—that very much depends upon the condition of the food 
which is presented as to its capability of being assimilated by the plant 
or animal. 
For example, aithcugh plants require a certain amount of potash and 
of phesphoric acid for their development, it has been conclusively proven 
that if the former be presented firmly locked up in chemical combina- 
tion, as in feldspar, it is practically unavailable to the plant. So, 
too, if phosphoric acid be introduced into the soil in the form of a 
very difficultly soluble phosphate, as powdered, apatite, that no good re- 
sults fellow from such application. So, too, leather chips, though rie 
in nitrogen, will for years withhold this important element from the 
plant, which, although adjacent to such supply, suifers from its inability 
to appropriate it. 
In like manner, with reference to animal focd, the real nutritive value 
of food depends rather upon the ability of the animal to digest and as: 
