NUTRITION, in the animal economy, is the repairing the continual loss which the different parts of the body undergo. The motion of the parts of the body, the friction of these parts against each other, and especially the action of the air, would destroy the body entirely, if the loss was not repaired by a proper diet containing nutritive juices, which being digested in the stomach, and afterwards converted into chyle, mix with the blood, and are distributed throughout the whole body for its nutrition.
Buffon, in order to account for nutrition, supposes the body of an animal or vegetable to be a kind of mould, in which the matter necessary to its nutrition is modelled and assimilated to the whole. But of what nature is this matter which an animal or a vegetable assimilates to its own substance? What power is it that communicates to this matter the activity and motion necessary to penetrate this mould? and, if such a force exist, would it not be by a similar force that the internal mould itself might be reproduced?
As to the first question, he supposes that there exists in nature an infinite number of living organic parts, and that all organized bodies consist of such organic parts; that their production costs nature nothing, since their existence is constant and invariable; so that the matter which the animal or vegetable assimilates to its substance is an organic matter of the same nature with that of the animal or vegetable, which consequently may augment its volume without changing its form or altering the quality of the substance in the mould.
As to the second, there exist in nature certain powers, as that of gravity, which have no affinity with the external qualities of the body, but act upon the most intimate parts, and penetrate them throughout, and which can never fall under the observation of our senses.
And as to the third, he conceives that the internal mould itself is reproduced, not only by a similar power, but by the very same power which causes the unfolding and reprodu-
tion thereof. For it is sufficient, he thinks, that, in an organized body which unfolds itself, there should be some part similar to the whole, in order that this part may one day become itself an organized body, altogether like that of which it is actually a part.