that insect is permeated by 1804 aëriferous tubes large enough to be visible, and it is probable that an equal number exist so small as to elude the sight, even when assisted by the most powerful glasses. "Surprising as this number may appear, it is not greater than we may readily conceive to be necessary for communicating with so many different parts; for, like the arterial and venous trees which convey and return the blood to and from every part of the body in vertebrate animals, the bronchiæ, (that is, the smaller ramifications of the tracheæ,) are not only carried along the intestines and spinal marrow, each ganglion of which they penetrate and fill, but they are distributed also to the skin and every organ of the body, entering and traversing the legs and wings, the eyes, the antennæ, and palpi, and accompanying the most minute nerves through their whole course. How essential to the existence of the animal must the element be that is thus anxiously conveyed, by a thousand channels so exquisitely formed, to every minute part and portion of it! Upon considering this wonderful apparatus, we may well exclaim. This hath God wrought, and this is the work of his hands."[1]
Adipose tissue, and Secretions. Although the former of these is not in immediate connection with any one organ more than another, but fills the splachnic cavity wherever it is not occupied by other substances; yet it so far bears a relation to the function of digestion and the nutritive organs, that it
- ↑ Kirby and Spence's Introd. IV. 65.
