CHAPTER XIII. 
ON THE FOOD OF ANIMALS. 
GENERAL CONSIDERATIONS. 
It is scarcely necessary to remind the reader that a constant supply of aliment is demanded 
by all living beings, from the earliest stage of development, from the germ-cell to that point in 
existence where the vital forces quit the fabric. The materials which are subservient to the 
development of a new being are derived, in the first instance, from the parent; the higher 
types of organization are strongly contrasted, however, with the lower, in both the animal and 
vegetable kingdoms. In the mammalia the new being has its parental connection continued for 
a long period, comparatively, during which it undergoes a variety of changes, all of which 
carry it upward to the form and semblance of the parent, so that, at birth, or when it is de¬ 
tached from the parent, it has acquired all the distinguishing attributes which belong to it as 
a species, so far at least as its physical organization is concerned. It has undergone its series 
of metamorphoses, and now, to complete its development, it has merely to acquire an increase 
of size. On the contrary, those animals and plants which rank low in the scale of organization, 
have but a brief parental connection ; they are cast out upon the world and thrown upon their 
own resources at an early day, and although these are sufficient, ordinarily, to secure the pre¬ 
servation and development of the individual, yet, as nature is solicitous for the preservation of 
the races, she secures this by multiplying to excess, as it were, their germs. The great class of 
invertebrate animals cast their ova profusely upon the theatre upon which they are to move ; 
and, as if to secure still more perfectly their continuance, they often multiply by buds and by 
division. The cryptogamia, as in the case of the puff-ball, send forth millions of spores, or of 
germ-cells, which are capable of developing an individual like the parent, whenever they rest 
upon a spot suited to their natures; but millions must perish for want of a suitable spot and 
medium, upon and in which to exercise their latent functions. 
In the higher vegetables, the germ-cell is surrounded by a store of nutriment, in which all fhe 
elements are concentrated which are essential to the first stage of development, or until it can 
strike its radicles into the soil, from which, in the future, it is to draw its entire supply. Fixed 
