The reasoning that was employed by the neurologists was, in like manner, founded upon the structure of the animal body. They asserted that nerves are dispersed through every portion of the muscular system; and that, although some parts are more plentifully supplied than others, yet that the quantity of nerve in each case is in proportion to the wants of the part, and are adequate to produce all the contractions of which it is capable. respect to the particular case of the heart, it was asserted that it possesses nerves, although perhaps less than some other muscles, and that the use of these nerves is, to re ceive the first impression of the stimulants, which ulti mately cause its contraction. As a proof of the general diffusion of nerves, it is affirmed, that there is no part of the body in which we can produce a contraction, where we cannot, at the same time, excite a sensation, for that it is impossible to insert the finest point of a needle, where WC shall not as easily feel pain or produce motion. Whytt seems to have had some difficulty in -accounting for the contraction of a muscular part after its removal from the body, and its separation from the nervous centre, and he found no better method of explaining this circumstance, than by supposing that the sentient principle is divisible, which in fact amounts to the position that different parts of the body can individually feel the impressions that are made upon them. It must, however, be admitted, that this consequence does not necessarily attach to the hypo thesis of the neurologists, for we allow that nerves may be affected, and may transmit the impression to the mus cular fibre, without produzing a perception.
:Many facts of perpetual occurrence were adduced, where muscular contractions were excited by causes which could only operate through the nerves, such as passions of the mind, and more especially the act of volition, whicn is the immediate cause of so large a proportion of our atotions. Numerous experiments were also adduced to prove that physical agents, hoth stimulants and seda n% vs, operate through the medium of the nerves. If the nerve which commtmicates with a muscle be immersed in a solution of iaurel water, or, on the other hand, be sub mitted to the galvanic influence, the muscle is as much or more affected, than if these agents were applied to the fibres themselves. There are, likewise, a variety of mor bid phenomena which favour the opinion that the nerves arc immediately concerned in muscular action, both those circu .stances which immediately affect the brain, or any part of the nervous system, and still more those which only operate through the intervention of the intel lectual functions.
And besides the numerous considerations which were adduced by ‘Vhytt and his contemporaries in favour of the nervous Ity pothesis, some elaborate experiments which were lately performed by Le Gailois, have been supposed to atibrd a still more direct proof of this doctrine. His
object was, to ascertain what are the respective effects of the different parts of the nervous system upon the powers of life; and, in the course of this inquiry, he conceived that he had demonstrated, that every muscular part is under the influence either of the brain or spinal cord, both of these parts being centres of nervous sensibility. One powerful objection to the hypothesis of ‘Vhytt is there tore removed, that the heart is capable of contraction after its separation front the brain; for, according to Le Gallois, the spinal cord is the part from which the heart derives its energy. He also endeavoured to show, by direct experiments, that when both the brain and spinal cord are removed or destroyed, all muscular contraction ceases; and he hence concludes, in opposition to the doc trine of Haller, that the nervous system is necessarily concerned in all cases of' muscular contraction. But not withstanding the elaburate and varied nature of Le Gal lois's experiments, many of his deductions have been call ed in question by Dr. W. Philip, who. from experiments no less elaborate, has attempted to show that muscular parts, and in particular the heart, can continue to contract for an indefinite period after the complete destruction of both the brain and spinal cord, so as entirely to destroy the force of Le Gallois's reasoning, and to go far towards establishing Haller's hypothesis.
We may therefore conclude, that, notwithstanding the weight of argument in favour of the opinion of the neuro logists, which has, at least of late years, given it a pre ponderance in the public estimation, they have not proved the point under discussion ; and that, although we admit the facts which they adduce, we may still doubt whether the nervous influence be a necessary step in the produc tion of muscular contraction In order to establish this point, we roust not only show that the nerves • ay be con cerned in the operation, but that their action is essential to the process. It is admitted that the nerve is frequently a necessary intermedium between the application of the stimulant and the contraction of the fibre, but is this al ways the case ? To this question we are disposed to reply in the negative ; and we conceive it to be clearly proved by Dr. Philip, that there are a large, class of muscular parts which have but little connexion with the nervous system, or are only occasionally subject to its influence. This is the case with the parts which are not under the control of the will and especially with the organs which are concerned in those functions, which in their ordinary and healthy action, do not produce perception.