" Animals and vegetables, then, agree in their equal necessity of extracting a certain sweet and saccharine fluid, as the basis of their support, from whatever sub, stances may, for this purpose, be applied to their respective organs of digestion.— Animal chyle and vegetable sap have a very close approximation to each other, in their constituent principles, as well as in their external appearance. In this re spect plants and animals agree. They disagree, inasmuch as animal substances possess a very large proportion of azote, with a very small proportion of carbon ; while vegetable substances, on the con trary, possess a very large proportion of carbon, with a very small proportion of azote. And it is hence obvious, that ve getable matter can only be assimilated to animal, by parting with its excess of car bon, and filling up its deficiency of azote.
" Vegetable substances, then, part first of all with a considerable portion of their excess of carbon, in the stomach and in testinal canal, during the process of di gestion; a certain quantity of the carbon detaching a certain quantity of the oxy gen, existing in these organs, as an ele mentary part of the air or water they con tain, in consequence of its closer affinity to oxygen, and producing carbonic acid gas ; a fact which has been clearly ascer tained, by a variety of experiments by M. Jurine, of Geneva. A very large surplus of carbon, however, still enters the animal system, through the medium of the lac teals, and continues to circulate with the chyle, or the blood, till it reaches the lungs. Here, again, a considerable por tion of carbon is perpetually parted with upon every expiration, in the same form of carbonic gas, in consequence of its union with a part of the oxygen intro duced into the lungs with every returning inspiration ; as is sufficiently established by the experiments of Mr. Davy, and other celebrated chemists ; while the excess, that yet remains, is carried off by the skin, in consequence of its contact with atmospheric air : a fact put beyond all doubt by the experiments and observa tions of M. Jurine, although, on a super ficial view, opposed by a few experiments of M. Ingenhouz ; and obvious to every one, from the well-known circumstance, that the purest linen, upon the purest skin, in the purest atmosphere, soon be comes discoloured. In this way, then, and by this triple co-operation of the sto mach, the lungs, and the skin, vegetable matter, in its conversion into animal, parts with the whole of its excess of carbon.— Its deficiency of azote becomes supplied in a twofold method. First, at the lungs ;.
also, by the process of respiration ; for we unitisrmly find, and the experiments of Dr. Priestley and Mr. Davy are fully con clusive upon this subject, that a larger portion of azote is inhaled upon every in spiration, than is returned by every suc ceeding expiration ; in consequence of which, the portion retained in the lungs must enter into the system, in the same manner as the retained oxygen, and per haps in conjunction with it ; while, in unison with this action of the lungs, the skin also absorbs a considerable quantity of azote, and thus completes the supply that is necessary for the animalization of vegetable food ; evincing, hereby, a don ble consent of action in these two organs, and giving us some insight into the mode by which insects and worms, which are totally destitute of lungs, are capable of employing the skin as a substitute for lungs, by breathing through certain spi racles, introduced into the skin for this put pose, or merely through the common pores of th e skimw About any such addition. al mechanism It is by this mode, also, that respiration takes place through the whole vegetable world, offering us another in. stance of resemblance to many parts of the animal consequence of which, insects, worms, and the leaves of vegetable equally perish, by being smeared over with oil, or any other viscous fluid, that obstructs their cutaneous orifices.
"But to complete the great circle of universal action, and to preserve the im portant balance of nature in a state of equipoise, it is necessary, also, to inquire by what means animal matter is recon verted into vegetable ; so as to afford to plants the same basis of nutriment which plants have previously afforded to ani mals." The process of putrefaction is shown to be that principle, which is to be regarded as a most important link in the great chain of universal life and harmony. See Good's Oration.
Coral lines, madrepores, millepores, and sponges, were formerly considered as lbs sil bodies ; but the experiments of Count Marsigii evinced, that they are endued with life, and led him to class them with the maritime plants. And the observa tions of Ellis, Jussieu, and Peysunel, have since raised them to the rank of animals. The detection of error in long established opinions, concerning one branch of natu ral knowledge, justifies the suspicion of its existence in others, which are nearly allied to it. And it WM appear, from the prosecution of an enquiry into the in stincts, spontaneity, and self-moving pow er of vegetables, that the suspicion is not without foundation.