Some physiologists, and those of no mean note, have considered the operations of the human frame as a circle of functions governed by mechanical organic laws, as we discover in an hydraulic machine, or automaton, so admirably formed, as by the mere force of its construction to perform and continue the vital motions.
In confutation of such an opinion we have nothing to do more than to introduce the words of the justly celebrated Doct. Whytt. “It seems” (says that writer) “to be incumbent on those philosophers who ascribe the motion of the heart to mechanical causes alone, to demonstrate the possibility of a perpetuum mobile, since as long as life lasts, an animal appears to be really such.” And it needs scarcely be added that perpetual motion is demonstrably without the laws of mechanics, and far above the power of mechanism. These considerations are, I judge, sufficient to put to rest all idea of an independent organic life: If others are wanted, it may be shewn that life, sense, and self-action, are inconsistent with the general properties of matter.
Others, writers of much reputation and celebrity, have contended for the existence of an innate independent principle of life in the muscles, and the plausible ingenuity with which these opinions were supported, could not fail to procure many advocates, and has indeed enlisted in its cause such a body of respectable talents, as to induce me to hesitate in my intended opposition: Nor do I now venture presumptuously to undertake the settlement, but shall only offer such reasons in objection to the doctrine, as have been suggested by various circumstances. It is not my intention to engage in all the minuteness of particular discussion. That would require more time and attention than I can at present devote to such an undertaking; but I shall content myself by briefly stating all the arguments which have fallen within my reading, most insisted on by the strenuous defenders of the above doctrine, and on which alone it seems to rest.—Then, by considering the arguments separately, endeavour to shew wherein they are fallacious, and point out the difficulties calculated, in my opinion, to oppose such specious reasoning.
The punctum saliens, or the first visible point in motion being the heart;
The birth of full grown Fœtuses without brains;
The performance of vital motions without consciousness;
Eggs freezing with more difficulty from the time they are first laid in proportion to their freshness;—and,
The contraction of muscles after removal from the body;—are I believe the points most relied on as evidence of an independent living principle in the muscular system, and which shall now be considered in the order detailed.
In considering the condition of animals in their nascent state, we may readily understand, that their rudiments, composed of a pellucid congeries of parts, will freely transmit the light, and as there is no analysis of the ray, or proper reflection of it, it can make on the retina no impression, nor convey to the mind any perception of the existence of distinct parts. Soon however the vital energy manifests itself in the formation of red blood, and the motion of a point which being capable of reflecting light presents to the senses marks of distinct organization. Yet from this we derive no evidence that this point is the first to possess life, but only, that it shews itself first, by means of its reflecting powers. And thus though we admit the proposition, it can assist the cause it was adduced to support but little; for the moving energy, we presume may be derived from co-existent parts. And indeed according to some accurate observers, the disproportionate head with other lineaments, appear visible some time before the heart is seen in motion.
That Fœtuses have in a few remarkable instances been ushered into a short lived existence without a brain, is advanced with some degree of elation by the supporters of the principle under consideration. Animals, from equally good authority, have been born without hearts: but will a few cases of lusus naturæ serve to disprove the importance of these organs to the animal economy? I fancy not; in either case above alluded to, we may suppose that the appendages performed, though imperfectly, the offices of their respective organs. And in those particular cases in which the brain is wanted, we may conclude with the learned physiologist, that it was destroyed by disease after the growth of the child, but left the nerves and ganglia (which Doctor Monro considers small or disproportionate brain) endowed with sufficient influence to maintain for a short period its life. If there be an independent vital principle in the muscles; why does not its power support those extremely rare cases, which unfortunately for the doctrine, as well as its advocates, do not generally survive birth any length of time.