“But while every organic creation tends to full development, that is, to absolute energy, or perfect life, still we find, that the organs of which it is composed are each reciprocally dependent on every other, for the possibility and degree of their peculiar action. At the same time, as these internal conditions of animated existence are severally dependent on certain external conditions, which, again, are not always fully and equally supplied; so it follows, that the life of every organized being is determined in its amount, and in the direction of its development, by the outward circumstances of its individual situation. For this reason, we see that every animal, and every plant, is dependent for its existence, and also for its perfect existence, on conditions both internal and external. “From this reasoning it may be conceived, how the several parts of the living whole reciprocally act and react. They are, in fact, cause and effect {255} mutually; and no one can precede another, either in the order of nature, or of time. Thus, in an animal, the digestive, and the absorbent, the sanguineous, the respiratory, and the nervous systems are at once relative and correlative. In like manner, in a plant, the same reciprocal proportion is found to hold between the roots and the stem, the branches and the leaves: Each modifies and determines the existence of all the others, and is equally affected by all in its turn. And as their several parts, by means of their union, constitute the organic whole; and as their functions, by the same means, realize the complement of life, which the plant or animal exhibits; it is evident, that every living individual is a necessary system, in which no one part can be affected, without affecting the other parts, and throughout which there reigns an intimate sympathy, and a complete harmony of perfection and imperfection.