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respiration and expression is confined almost entirely to the proboscis.
As the anatomy of the nerves of the trunk of the elephant bas been hitherto very incorrectly given, I shall here offer a description of them, from notes taken at the dissection of a young
The portio dura was found emerging from the parotid gland, as in other mammalia. It gave off some descending branches to the neck, but passed from behind the jaw to the proboscis, almost as an entire nerve, and of the size of the sciatic nerve in man. In its course, it had only given some small branches to the muscles of the eye, to those of the ear, and to a small muscle which corresponds with the platysma. Before it passed into the substance of the proboscis, it united with the second division of the fifth pair, which comes forward from the infra orbital bole, in two large branches. The two nerves, being then closely united, passed between the layers of the muscles which form the greater mass of the trunk. The portio dura became quickly diminished in size, as it gave off its branches in great profusion to the muscles; but the fifth was continued down, as a very large nerve, to nearly the extremity of the trunk, in this respect resembling the nerves to the fingers in.' man. On making sections of the proboscis, near its extremity, a great number of the branches of the fifth were seen in its substance.
A few branches of the portio dura ran to the valvular apparatus in the upper part of the trunk; but this peculiar structure was supplied principally by a branch from the fifth pair, which winded round under the orbit.
If we compare the anatomy of the facial respiratory nerve in the various classes of birds, we shall find its distribution to be analogous to that of the same nerve in the different tribes of quadrupeds. In the game-cock, a few branches of the nerve pass to the muscle connected with the loose skin under the jaw, which is dilated in crowing ; the greater number being distributed on the muscles of the neck, which cause the elevation of the feathers when this bird puts himself in an attitude for fighting. But in the duck, which, when enraged, bas little or no power of expression, the same nerve is not larger than a cambric thread, and passes only to the muscle under the jaw.
As so many observations are already before the public descriptive of the effects produced by cutting this nerve, * I shall only submit the question, whether the numerous experiments that have been made do not, when taken into account with the
See the Philosophical Transactions, and the communication by me to this Journal in December last. The question of the apparent sensibility of this nerve is alluded to in the Number for October.
comparative anatomy of the nerves of the face, prove that the use of the portio dura in man, is to combine and regulate the action of all those muscles of the face which are in any way connected with respiration.
The nerve next in order is the EIGHTH. We should consider the three nerves of which it is composed as distinct, although they be united in function.
The first is the GLOSSO PHARYNGEAL, and is marked 8 in the Plan. The origin and distribution of this nerve distinctly point out its use, - viz. that of combining the actions of the tongue and pharynx in deglutition. Its power over the pharynx has been shown by several experiments, the results of which were very curious, and corroborative of the views deduced from comparative anatomy.
The next, the PAR VAGUM, is perhaps the most interesting nerve in the body. It is marked i in the Plan. Two distinct branches pass from it to the larynx ;-viz. the supeRIOR LARYNGEAL, marked 2 ; and the inFERIOR LARYNGEAL, or RECURRENT, 3. We see also the PULMONIC PLEXUS, 4; the CARDIAC PLEXUS, 5; and the GASTRIC PLEXUS, or corda ventriculi, 6. The ESOPHAGEAL PLEXUS, though not marked by any figure, may be easily discovered. When we examine this nerve mi. nutely, we find that it is not only intimately connected with all the nerves seen in the accompanying Plan, but also with the Sympathetic.
To go into the full consideration of the anatomy and conpexions of the par vagum, would far exceed my limits; but here I may observe, that, unless we examine the comparative anatomy of this nerve, we shall be very apt to draw erroneous conclusions from experiments made upon it, in the mammalia. Indeed, if we examine what has been deduced from many of the experiments lately made upon the par vagum, we shall be led to suspect that the experimenters did not take into consideration the fact, that this nerve, exists only where there is a necessity for a combination between the functions of the stomach and of the lungs. For example, it has been attempted, by experiments, to prove that the secretion of the gastric juice depends on the par vagum; forgetting, apparently, the well-known fact that, in many animals which have the power of digesting very crude substances, there is no nerve of this kind.
While upon this subject, I may take the opportunity of stating my belief that certain opinions, which are at present held upon the functions of the viscera of the thorax and abdomen, are the means of keeping up many erroneous notions on the uses of the nerves. To me it appears that the principal object of many of the late experiments has been to discover the power which enables the heart to contract, or the glands to
secrete. This power has, I believe, been generally ascribed to the nerves which are seen passing into these viscera; but, when we find that a stomach which secretes gastric juice, a pancreas saliva, a liver bile, a kidney urine, are all furnished with the same nerves, and that these are not only the nerves of the lungs and of the heart, but also of the muscles of the pharynx and larynx, we are, I think, forced to conclude that this nerve is not for conveying a power or principle to these parts, which shall enable them to perform their several offices. Indeed, we may even believe that these organs have a power independent of the par vagum, or perhaps of the brain, since we find them capable of performing their several functions, not only in animals so low in the scale of existence as to have neither brain nor nerves, but even in monsters where a great part of the neryous system is deficient.
The attempt to discover what is the principle by which the different glands are empowered to secrete certain fluids, would be fruitless: but still this should not prevent us from investigating the laws upon which the due performance of those actions depend.
I am aware that this is a very difficult subject; bat, as certain clear and demonstrable facts can be substantiated, I may be permitted to allude to the question, though in a cursory manner.
It will probably be acknowledged, that the body of the more perfect animals is so constituted that each organ has a power, to a certain extent, of performing its peculiar function; but that this function will not be properly performed, unless the combi. nation or relation of the organ to the other parts of the body be perfect and uninterrupted ; and, moreover, that the undue performance of the functions of one organ will have a certain effect upon those of others. Still it does not follow that any virtue is actually conveyed from one viscus to another, but only that they are united together so as to constitute a circle of actions mutually dependent on each other. Indeed, we know that the secretion of gastric juice by the stomach is imperfect, unless the actions of the lungs be properly performed; and, on the other hand, that our endeavours to resuscitate an animal apparently drowned, will fail if there be poison in the stomach.
There can be little doubt that the combination between the different organs is kept up by nerves. In the mammalia, we see the par vagum pass from the lungs to the stomach; and we may assume that it is the bond of union between their func. tions, since neither those of the one viscus nor of the other are perfectly performed if the nerve be divided.
Seeing that the gastric juice is not secreted when the par vagum is cut, we are at first view inclined to infer that the power of secretion depends on the par vagum; but, when we. find, by the investigations of comparative anatomy, that the stomach may be entirely independent of such a nerve, we are compelled to give up this opinion. Indeed, the arguments in favour of it are still further weakened by finding that if, after the par vagum has been cut high in the neck so as to disturb the functions of the lungs, respiration be assisted by any artificial means, the functions of the stomach will be partially restored.
Perhaps the only legitimate conclusions we can draw from the observation of such facts, are that the par vagum is the mediom through which the several important organs are knit together and associated in their function, and by the injury of which the organs themselves are hurt and deranged. Digestion, respiration, and circulation, are not separate functions, but the different stages of one great operation, “ nutrition," necessary to life; and for this purpose the organs are bound by sympathies, which cause them to act in unison, and by which they become mutually dependent. Hence the injury of one has an effect upon the others, and the destruction of the medium of connexion disturbs the whole economy.
In this inquiry it is quite admissible to examine how far those who have beld different opinions have been correct in their views of the anatomy of the nerves, and particularly in the assumption of the data from which they have drawn their conclusions regarding the uses of the par vagum. In doing so, we sball discover that the same deductions have been drawn from experiments where the par vagum and sympathetic have been cut, as from those where only the par vagum was divided.*
I shall not make any further observations at present upon this question, but submit, that since, in the more complicated animals, (as in the mammalia,) the par vagum passes to the throat, the larynx, the beart, the lungs, and the stomach, its use is probably to connect and combine, into one great system, these several organs,-each of which has the power of performing, to a certain extent, its own peculiar function. And hence it naturally follows, if the nerve be divided, the connexion be. tween all the organs, and also betwixt them and the external inuscular apparatus, upon which the perfection of the economy of each depends, will be destroyed.
Although I will not at present enter into the full consideration of the symPATHETIC, I shall make a few observations on the prevailing opinions regarding its anatomy and uses. +
The par vagum and sympathetic are so closely united together in the neck of the horse, that it is exceedingly difficult to separate theni, even in the dead animal
. * On anuther occasion, I propose to show that the anatomy of the sympathetic has been so erroneously described, not only in the thorax, but also in the neck and head of many of the lower classes of animals, as to entitle us to deny that any of the modern theories on the uses of this nerve are founded on correct views of its anatomy.
It will at once be admitted, that the descriptions most commonly given of late of this nerve are copied from the works of Bichat. Now I do not hesitate to state that the description, as given by Bichat, is incorrect; and that it does not correspond with what is found upon dissection, nor with that given by the most eminent anatomists who preceded him.
If we examine the manner in which the nerves arise from the spinal marrow, we shall find that each nerve has not only a double root,-i. e. one from the anterior, and the other from the posterior column of the spinal marrow,-but that they are also all united with, or give off a branch to the sympathetic. This union, or origin, of the sympathetic from the spinal nerves appears to have been entirely overlooked by Bichat. We may however presume that, had he lived, he would have given up the idea of considering the sympathetic as a part entirely distinct from the system of the spinal nerves; for it is a striking and curious fact, that, in the edition of his “ Anatomie Descriptife," pub. Tished in 1802, the editor says, “ Nous reprenions ensemble le systéme nerveux des ganglions et c'étoit le soir même ou nous avions commencé le ganglion cervical superieur que Bichat fit cette funeste chute qui determina sa dernière maladie."
It is, perhaps, not assuming too much to say, that since Bichat was incorrect in his views of the anatomy of the sympathetic nerve, it follows that not only his own ideas on the ganglionic system are untenable, but that also all the conclusions from ex. periments, which have been instituted in the belief that his observations were correct, are also liable to objections. I shall not here state the conclusive arguments that may be offered in contradiction of the opinion, that the system of the sympathetic is similar to the nervous cords seen in the lower anii als; but I shall merely ask how far the theory, that the actions of the heart depend more upon the sympathetic than on any other nerve, can be correctly founded, when it is easy to demonstrate that, at every intercostal space, the beart is united, through the sympathetic, with the spinal marrow. The observation that the sympathetic has been found perfect in monsters in which the spinal marrow was deficient, affords no argument in favour of the sympathetic being isolated from the other parts of the nervous system; for, in such creatures, we generally find also the spinal nerves, which are by all acknowledged to bave their origin from the spinal marrow.
The difficulty of discovering the power by which the various glands secrete the different fluids, has been already noted. The same difficulties are presented when we inquire into the causes of the actions of other important organs. For example, if we cut out the heart, and thus at once, in the most effectual way, separate it from the nervous system of the body, we shall find