556 The American Naturalist. [July, 
into animal products of greater value. This simile, which is 
often made, is of greater significance than at first sight would 
appear, and if breeders will keep in mind the fact that they 
are, in effect, providing machines for doing work in the man- 
ufacture of meat, milk, wool, muscular power, or other animal 
products, from the raw materials derived from the soil, the 
means of improvement will be more readily understood. 
From this point of view the breeders of live stock should 
have a deep interest in the general progress of agriculture, as 
any improvement in crop growing must be to their advantage, 
from the larger supply of raw materials for the manufacture 
of animal products, which should increase the demand for 
animal machines to perform the work with the greatest econ- 
omy, and at the same time turn out a finished product of a 
quality than can be disposed of at renumerative prices in the 
market. 
This simile of a machine makes apparent the fallacy of the 
old notion that the animal that eats the least is the best for 
the farmer. It would certainly be a poor recommendation for 
a machine to say that it could work up but a small amount of 
raw materials. The object of the farmer is, profit, and in 
every department of production the aim should be to obtain 
the largest net return from the raw materials he has to dispose 
of. The more the animal machine can do of useful work, the 
greater its value to the farmer, if the results are obtained with 
the greatest economy. 
. Another popular error will be readily corrected by looking 
upon animals as machines for doing work. The notion has 
too generally prevailed that animals are composed simply of 
flesh and blood and bones, etc., and that when they are furnish- 
ed with food containing the materials which enter into the 
composition of their tissues, it would, in some mysterious way, 
be converted into animal substances. This is, however, a par- 
tial or one-sided view, that does not represent the whole 
truth. 
. Farmers are constantly dealing with the forces of Nature, 
and a knowledge of naturallaws cannot fail to aid them in 
their mastery. The applications of the law of the conserva- 
