DISTINCTIVE CHARACTERS OP ANIMALS. 
27 
stomach, being extemporized, as it were, on each occasion that 
aliment is ingested; and an anal orifice being extemporized 
in like manner, when the indigestible residue has to be cast 
forth. All true Animalcules (§ 133) have a proper mouth, 
into which food is drawn by the current created by the cilia 
(§ 45) wherewith it is fringed; and this mouth leads to the 
general cavity of the body, within which the food is subjected 
to the digestive process, hi Zoophytes (§ 121) which possess 
a proper stomach, this organ forms so large a part of the 
animal, that its entire body may be almost said to consist of 
the stomach and of the prehensile appendages by which it 
draws in its food. Eut in all the higher tribes, the stomach, 
with the alimentary canal proceeding from it, are suspended 
freely within the general cavity of the body; and we shall 
find that the space that surrounds these viscera is extremely 
important in the economy of all but vertebrated animals, as 
being a sort of reservoir into which the nutrient materials 
prepared by the digestive process first transude, and from 
which it is carried into the remoter parts of the system. In 
vertebrated animals, this cavity—called in them the peritoneal 
cavity, from its being lined with a serous membrane (§ 28), 
termed the peritoneum—As not subservient to the same pur¬ 
poses ; the nutrient materials being taken up from the walls 
of the digestive cavity, both by the blood-vessels and by 
special absorbents, and being by them carried into the current 
of the circulation. It is obvious that until they have found 
their way, through one or other of these channels, into the 
general system, the nutrient materials introduced as food into 
the stomach of an animal are not within its body, properly so 
called, any more than a fluid is within a plant when it bathes 
the exterior of its roots, or within an entozoon when in con¬ 
tact with the soft surface of its integument. In each case, 
the absorption of the fluid is first requisite; and it is with 
this that its application to the requirements of the living 
body really commences. 
9. Eut further, when we compare together, not the lowest, 
but the highest members of the Vegetable and Animal king¬ 
doms respectively—those in which their respective attributes 
are most characteristically displayed,—we find that they 
present such differences as to render it quite impossible to 
confound the one with the other. Although it is easy even 
