페이지 이미지

should be noted that the olivary bodies are more voluminous in man than in any other animal, and that the nerves of the pharynx, larynx, and the tongue issue from the olivary fasciculi, which by the mediation of the hypoglossus thus act on enunciation."

Van der Kolk says :—“Immediately after I had discovered the special fasciculus connecting the corpora olivaria with the nucleus of the hypoglossus I suspected that the very delicate combinations of motions in the human tongue, in articulation and speech, might afford an explanation of the much greater size of the olivary bodies, and of the more intimate connection with the nuclei of the hypoglossus. For speech and the articulation of words require such a multitude of varying combinations of its muscular movements, that it cannot appear strange that two auxiliary ganglia* should be required for the performance of these functions." That the corpora olivaria are organs for the articulation of the voice is no mere conjecture, but confirmed by facts, several of which are cited by him.

From the intimate connection existing between the facial nerve and the olivary bodies, as shown by Retzius (Müller's Archive, 1836), the olivary bodies may also be considered as central organs for the mimic expressions in the countenance.

Semicircular Canals. The experiments performed by Flourens on these organs presented the following phenomena :-Section of the horizontal semicircular canal in a pigeon induced a tendency to turn to one side ; section of a vertical canal was followed by a violent vertical movement of the head; section of the anterior vertical canal caused the animal to make continued forward “somersaults." Flourens hence concludes that the nerve supplying these canals does not minister to the sense of hearing, but to the direction of the movements of the animal.

In the sitting of the Academie des Sciences, Feb. 17, 1862, Flourens refers to this subject as follows :-" There are but four principal movements in man; from right to left, from left to right, backwards and forwards, each of which corresponds only to the direction of a semicircular canal; the movements from right to left, and from left to right-to the two horizontal canals, one right and the other left. The movement backward to the antero-posterior canal; the movement forward to the antero-anterior canal. These great phenomena, not yet explained, have engaged my attention for thirty years, and I trust I shall succeed in fathoming them."

• The accessory olivary ganglia, discovered by Stilling, appear to be the centres for the process of deglutition.

These experiments, showing that there is a constant relation between the direction of each semicircular canal and the direction of the movement have been repeated by Brown-Séquard, and recently by Czermak; the former concludes that the auditory nerve is a veritable centre. Flourens does not say that the cause of the movement lies in the canals, but lies farther off in the encephalon

The Pineal Gland, which has derived its name from resembling the cone of a pine, and has, from its central position in the brain, been considered by Descartes as the throne of the soul, has long lost caste, since it was found that the sand contained in it is not merely found in the brains of idiots but in the brain of every adult. Nor is the calcareous substance peculiar to the pineal body, but is found in other parts of the cerebrum, and from its resemblance to starch corpuscules, termed by German physiologists corpora amylacea. Indeed by some physiologists the pineal body is not considered to consist of nervous tissue at all, but is like the pituitary body, formerly believed to discharge its excretions through the nostrils, and thus to clear the brain, simply placed among the ductless glands. It is scarcely necessary to state that the functions of these bodies are altogether unknown.

The Medulla Oblongata. Of all parts of the human body," says Schroeder van der Kolk* (p. 87), “there is not one which is of so great moment to the existence and continuance of life, and to the maintenance of the most different and important functions of the system, uniting in a small space, and, as from a central point, directing so much that is various in aspect and really diverse as the medulla oblongata. . . . . Here is, in fact, the nucleus and the central point, whence most phenomena proceed; here the seat of perception or sensation seems to lie; violent pain, by reflex action here, produces groaning; here reflex movements pass over to the other side ; here is the centre of automatic respiratory functions and of deglutition; hence the nervus vagus derives its remarkable influence upon the heart; and finally, an irritated condition of this part produces excitation of the sexual organs, and even appears to have some influence on the action of the kidneys. That the medulla oblongata is the seat of perception can scarcely any longer be a subject of doubt. Not only is it known that the brain itself is insensible, but while the nerves of sensation in the spinal cord pass upwards, the trigeminus descends to the medulla oblongata, that is, to the seat of perception." (Page 93.)

* On the Minute Structure and Functions of the Spinal Cord and Medulla Oblongata. Translated by W. D, Moore. London : 1859.

But, stof perceptshriekinemarily tee

But, strange to say, whilst Van der Kolk considers the medulla as the seat of perception and sensation, he invalidates his assumption in his remarks “on shrieking"-" There are, in fact, many involuntary actions, which we ordinarily regard as voluntary; for example, shrieking with pain. This shrieking appears to be merely the effect of a reflex action on the upper part of the spinal cord, or medulla oblongata. .... Hence it follows that in vivisections so many incorrect inferences are drawn as to feeling or perception in animals. If the brain is cut off above the pons varolii, and the fifth pair of nerves be strongly stimulated, the animal will cry out, although without consciousness, without perception, and without feeling of pain.(Page 77.)

Here we may well ask, if the medulla, and not the brain, is the seat of sensation, how does it come to pass that the removal of the hemispheres abrogates sensation, though the medulla remains intact? The above fact would rather lead to the inference that the seat of perception is in the hemispheres, and not in the medulla. We simply draw attention to this glaring contradiction, without in any way denying that the medulla may be a centre of sensation and motion, specially in animals possessing no brain, properly so called. But not merely the medulla oblongata, but the spinal cord, properly so called, has been considered as a real sensorium.

Sensorial Functions of the Spinal Cord. Many observations have abundantly proved that animals may feel and will after the removal of the hemispheres. It is also remarkable that this removal does not produce the same effect in all animals. Thus, rabbits and guinea pigs were seen to run about after the operation, and the latter are even said to defend themselves, when irritated.

The clearest proofs of sensation and volition are, however, exhibited by reptiles. “Twenty-four hours,” says Volkmann (Wagner's Handwörterbuch, i., 579), “after I had removed the large hemispheres from a frog it skipped about in the room, endeavouring to conceal itself behind a chest of drawers, and though pushed back several times with the hand or foot, it always returned. Placed into a pot it did not spring forward, but upwards, as if it saw the aperture. Motions of this kind cannot be called reflex, for such actions an excitation is requisite, which primarily proceeds from the periphery to the centre, and secondarily from the centre to the periphery.”

A large alligator, four feet long, being decapitated, the headless trunk, as on many former occasions, performed numerous actions, indicative of volition, sensation, and intelligence. The body curved VOL. I.-NO. III.


in a manner so as to recede from the offending agent, and the limbs were directed so as to remove it. From its actions, far more impressive than words, it was evident that it judged accurately, as to the degree, duration, and place of painful or painless impressions. (Dr. Dowler on Nervous Action.)

E. Pflueger* has published a very interesting monograph “ on the sensorial functions of the spinal cord,” not only in reptiles but in mammals, and also in man. This theory has only received a partial assent from physiologists.

The Vital Knot (point vital, næud vital). There is a small V-shaped spot of grey substance in the medulla oblongata, resulting from its bifurcation, which is by Flourens pointed out as the centre of life, because instant death is the consequence of its destruction.

Dr. Brown-Séquard, however, considered that Flourens has erred, in ascribing this function to this part, inasmuch as the removal of the neud vital” does not immediately produce death, nor is voluntary motion and sensation instantly destroyed.

Flourens replies :--"Physiologists have asked me to indicate the precise spot of the point vital.'” I answered, “ the point vital” is indicated by the V-shaped gray substance. They asked me for an external mark, and I gave it. But I never imagined they would take the external mark for the spot itself. It seems, however, that some have committed this mistake; they removed the V-shaped grey substance, and were astonished that the animal did not die. The V-shaped substance has nothing to do with the “neud vital,” which is situated beneath it. The “næud vital” is double, as every thing is double in the nervous centres. In order that life should cease, both halves should be divided to an extent of two millimetres and a half each, five millimetres for the two. A transversal. section, deep enough, of five millimetres at this given spot, is sufficient to destroy life at once.

From the conflicting opinions entertained by physiologists, in regard to the function of most parts of the encephalon, it cannot but be admitted, that despite of numerous experiments, cerebral physiology is still in its infancy. The most essential requisite is, no doubt, in the first place, a microscopic anatomy of the brain, which is far from being complete; so that Gratiolet, one of the most eminent cephalotomists of the day, says—" Let us confess that in our ignorance of the true structure of the medulla, the peduncles, and the optic thalami, the question is abandoned to the speculations of phy. siologists.” How long it may be before cerebral physiology shall acquire a firm basis, and reach that state of perfection which may enable us to solve any of the mooted problems, we cannot at present say. In the mean time, we must continue searching for corporeal parallels to psychical manifestations, and collect all possible information relative to cerebral structure, both of individuals and of the different races of mankind.

* Die Sensorischen Functionen des Rückenmarks. Berlin : 1853. See also G. H. Lewes' Physiology of Common Life, and papers read before the British Association 1858, for the details of a theory generally in accordance with that of Pfüger.


By A. A. FRASER, Esq., F.A.S.L.

It is somewhat singular that so long an interval should have occurred between the revelation of the wonders of the Pacific by Captain Cook -its practical discovery in fact-and the occupation, for colonization or commerce, of certain islands and groups of islands, which he proved to contain all those elements which can be welded into wealth and prosperity. It is true that the famous Botany Bay was examined a few years after the great navigator had visited it,—the spot of his landing being marked by a plate and inscription,—but more than half a century from that date passed before the first emigrant ship ran into Queen Charlotte's Sound, New Zealand, with a number of settlers to occupy a country with which Captain Cook was delighted, and which both the Americans and the French thought of colonizing before us.

The aborigines of Australia having familiarized Europeans with their manners and customs, the white rovers soon faced the feared and long-dreaded New Zealander, or Maori, and anchored in his harbours, fished on his coasts, ascended his rivers, and soon boldly ventured on more intimate relations. It was bold spirits who colonized Australia, and the boldest of them who settled amid the can

« 이전계속 »