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Dr. Lockhart Clarke says that in most of them at least seven distinct and concentric layers may be distinguished. Dr. Clarke says that the other convolutions differ from those at the extremities of the posterior lobes, not only by the comparative faintness of their several layers, but also by the appearance of some of their cells; he also adds that at the extremity of these posterior lobes the cells of all the layers are small, but on proceeding forward from this point, the convolutions are found to contain a number of cells of a much larger kind; again, in the insula which overlies the extraventricular portion of the corpus striatum, he finds a great number of the cells are somewhat larger, and the general aspect of the tissue is rather different. M. Broca has also studied the minute structure of the cerebral convolutions, and has ascertained that the relative thickness and general disposition of the six layers recognised by M. Baillarger differ notably in the divers regions, and although his researches are not definitely terminated, he ventures to assert that the structure of the convolutions of the insula differs from that of the frontal convolutions and of the hippocampus major. I can nowhere find that any difference has been noticed in the convolutions of the two hemispheres.*
* Since the above was written, Dr. Broadbent has kindly favoured me with a private communication in reference to his recent researches as to the course of the fibres of the brain, so far as his observations bear upon our subject. Dr. Broadbent's dissections shew that the structure of the third frontal convolution is peculiar, inasmuch as it receives fibres from a greater variety of sources than any other convolution; and he adds that although this anatomical fact does not throw any particular light on the function of the third frontal convolution, it seems to indicate that it is an important part of the hemisphere. In comparing the two sides of the brain, Dr. Broadbent has usually found the third frontal convolution larger on the left side than on the right, and the brain of a deaf and dumb woman, he noted that this gyrus was small on both sides, and especially on the left.
PHYSIOLOGY.— What does physiology say to Dax's theory, which has in its favour the undoubted frequency of aphasia with right hemiplegia, as compared with loss of speech as an accompaniment of sinistral paralysis? This may possibly be explained by the anatomical difference between the origin of the right and left carotids, making the supply of blood to the left side of the brain more direct than that to the opposite hemisphere, and by increasing its functional activity, thus rendering the left hemisphere more adapted for the exercise of speeeh.
It would be interesting to know what effect would be produced upon speech by cutting off the direct supply of blood from the left hemisphere. Dr. Wm. Ogle quotes a case where the left common carotid artery was tied by Mr. Lee; the patient died in two days, and in the interval between the operation and his death he was speechless.* In the Medico-Chirurgical Transactions for 1859 and 1865, are recorded four cases in which the left common carotid was tied by Mr. Nunneley of Leeds; speech was unaffected in three instances, but in the fourth, great difficulty in speaking was noticed on the sixth day. Since the publication of these cases Mr. Nunneley has tied the common carotid in two other instances, and he writes to say “in neither of these was there any difficulty in speech, either as regards the idea or the power of utterance.”+
* St. George's Hospital Reports, 1867, p. 111.
+ On looking over the published cases of ligature of the common carotid artery, I find that one of the earliest instances is one where the
An important question for inquiry is, the frequency of the coincidence of left hemiplegia with aphasia in left-handed people. I can only find two instances of this combination ; one recorded by Dr. Hughlings Jackson,* and the other by Dr. Wadham. The subject of Dr. Wadham's case, a young man of 18, belonged to a left-handed family, as four of his brothers, as well as himself, were left-handed. This case having terminated fatally, there was found to be an almost entire absence of the island of Reil on the right side, its place being occupied by a large cavity containing a little fluid and a small amount of broken-down brain-matter; the left hemisphere was perfectly healthy.t
As a cognate question, I would ask, why are we right-handed ?
Is the human race right-handed by mere accident? Although there are a few left-handed people in the world, the immense majority of persons use the right hand for every mechanical act. Is this a question of education or of mere imitation? If we concede this, we must admit that our ancestors in remote ages must have been influenced by some cause connected with the organization itself; if it were a mere chance that had determined the choice of the right hand, we should find some left-handed races in certain parts of the world, which, I believe I am right in stating, is not
left common carotid was tied in 1815, by Mr. Dalrymple, the well known Surgeon of the Norfolk and Norwich Hospital, for aneurism by anastomosis of the left orbit. It this case speech seems not to have been affected, for it is stated that “a few minutes after the patient was placed in bed, she declared that her head no longer felt like her old head, as the noise by which she had been so long tormented had now ceased.”—Medico-Chirurgical Transactions, 1815, v. 6.
* Medical Times, Aug. 25, 1866.
GRATIOLET'S STATEMENT DENIED BY CARL VOGT. 165
Besides, this question may be set at rest, says M. Broca, by the consideration “that notwithstanding all their efforts to counteract it, there are left-handed people, who remain left-handed, and one must, in their case, admit the existence of an inverse organic predisposition, against which imitation, and even education, cannot prevail."'*
The study of Embryology may assist us here. An eminent foreign physiologist, Gratiolet, says that in the development of the brain, the frontal convolutions of the left hemisphere are in advance of those of the right, and that the left are already properly figured, whilst the right are not yet even visible. Thus according to Gratiolet the left hemisphere, which holds in its dependence the movements of the right limbs, is more precocious in its development than the opposite hemisphere, and thus the young child uses by preference the limbs of which the innervation is the most complete, or in other words he becomes right-handed. From the cause which thus makes us use the left hemisphere for mechanical acts, may arise the circumstance of our using it in perference for speech, and we thus become left-brained-gauchers du cerveau—to use M. Broca's expression. But is this theory of the early development of the left frontal convolutions true? Gratiolet says it is; Carl Vogt, an equal authority, denies it. This is an extremely interesting and important question, about which very few are in a position to give a valid
* At the discussion on aphasia which took place at the Norwich meeting of the British Association, Professor Broca alluded to the circumstance that all birds perched on the right leg ; Dr. Crisp, on the other hand, said that this peculiarity was confined to Grallæ, and he believed it was a question of equilibrium, and that the bird was compelled to take this position from the greater weight of the liver.
opinion, and I regret I can quote no British authority in reference to it.
COMPARATIVE ANATOMY.—Does the study of Comparative Anatomy throw any light upon our subject? Here we must inquire whether language be the exclusive prerogative of man? Some would answer this question in the negative, and M. Lemoine, in the work to which I have already alluded, devotes a chapter to Le Langage des Bêtes.* The remarkable faculty of imitation and of gesticulation possessed by the Ape tribe, together with their power of giving expression to a variety of emotions, would seem to imply the possession of a faculty, to which one might properly give the name of language. Leconte, in his “History of China,” says of an Ape which he saw in the Straits of Molucca, that its actions so strongly resembled those of Man, and its passions were so lively and significant, that a dumb person could scarcely make himself better understood, or more plainly express his ideas and desires.
Max Müller, speaking of this subject, says, “Speech is a specific faculty of man. It distinguishes him from all other creatures; and if we wish to acquire more definite ideas as to the real nature of human speech, all we can do is to compare man with those animals that seem to come nearest to him, and thus try to discover what he shares in common with these animals, and what is peculiar to him, and to him alone.”
* A distinguished French anthropologist, M. Coudereau, says that articulate language in man is neither an innate nor an exclusive faculty; that man acquires the faculty of speech by his memory, labour, and imitation—the parrot does no more; that from a linguistic stand-point, this faculty is in its nature identical in man and animal.