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must be made for the confirmation or the setting aside of these views, to the brains of the most rational among Mammals; since, if such should exhibit a high development of the transverse convolutions, whilst in species merely allied to these, whose habits appear to be governed by instinct alone, the transverse convolutions are correspondingly small, a very important probability will be afforded in favour of Mr. Dunn's hypothesis.
We believe that no intelligent psychologist will now be inclined to dispute that the true difference between Man and other Mammalia rests specifically and fundamentally on ).he greater number and the higher nature of his intellectual powers and his emotional states; the less elevated forms of both being common to him with animals much lower in the series. Hence, in Mr. Dunn's opinion, the tripartite division of the Cerebrum into lobes, and the order and succession of their development, point to some such inferences as the following:
1. In animals which only possess the representatives of the anterior lobes, these must necessarily be the seat of the mental faculties which such animals manifest.
2. If the posterior lobes be exclusively Human, they must be the seat of exclusively human faculties.
3. The middle lobe may perhaps be regarded as the seat of those affections which are more of a personal or individual character, from the circumstance that it is more directly connected than the others with the sensory apparatus, and especially, by the olfactory peduncles, with the sense of smell, which is the guiding sense to the gratification of the first instinctive want, or craving for the conservation of existence, of the young Mammal. Hence the love of life may be regarded as one of the primordial forms of cerebral activity, and may be fairly located in the primordial convolutions.
As we have already expressed our opinion upon several of the points involved in Mr. Dunn's statement of doctrines, we shall limit ourselves to a general statement of what we believe to be the present aspect of the question. We fully agree with him as to the method of the inquiry, and believe that, rightly followed out, it will lead to important results. But it appears to us far more difficult than he would seem to suppose, to determine in the first place what are the mental phenomena in the lower animals which are homologous with those of man; and secondly, to determine what are the homologous parts of the cerebral structure. We have pointed out on former occasions what a fundamental difference exists between the instinctive and the intelligential sources of operations that may really be in themselves of the same character; the action in the former case being the direct response to an external impression, which only involves the sensori-motor apparatus, whilst in the latter it is the product of cerebral activity to which external impressions may only afford the remote stimulus. The architecture of the bee as compared with that of man, the migrations of the locust in search of food as compared with man's voyages across the ocean with the like object, the nurture of the eggs and pupae so remarkable in the ant as compared with the thoughtful care bestowed by the well-trained human mother upon her offspring, are examples of the difference to which we allude. In the case of Iuvertebrated animals, we have not much difficulty in coming to the conclusion that even the most striking manifestations of adaptiveness do not indicate that the source of this adaptiveness exists in the mind of the animal; since it may be fairly set down, whenever it is the constant habit of the species, to the account of its bodily organization, like the equally adaptive actions of coughing, sneezing, &c., in ourselves. But when we have evidence of the dawning of the truly rational powers, corresponding with the progressive evolution of the cerebrum, there comes to be a great difficulty in separating the instinctive or intuitional from the intelligential direction of the actions. We do not say that this difficulty is insurmountable; we believe that it may be in great degree got over by careful observation and judicious analysis of facts; but at present we feel assured that it is premature to base any induction upon the comparison of the psychological manifestations of the lower animals with our own. We may take a fundamental question of visual perception as an illustration of our remarks. sWe have lately been engaged on a careful analysis of the sources of our appreciation of the solid forms and relative distances of objects; and we have come to the conclusion that even that which we gain through the medium of binocular vision, and which comes to us so directly and instantaneously as to have much of the character of an instinct, is really the result of long experience in the interpretation of visual, tactile, and muscular sensations; the only part which can be regarded as an original intuition being the sense of direction, by which we instinctively refer an impression made upon the retina to an external source having a certain related position in space.* Now, we think there is ample evidence that the appreciation of the exact distance of near objects is an original and not an acquired intuition with many of the lower animals; or rather, we should say, that the movement which results from the visual impression does not acquire any perceptive appreciation at all. And this being the case, we should refer the resultant action, which in man has a cerebral source, to the most direct prompting of the optic ganglia. Now it is not a little confirmatory of this view, that, if M. Gratiolet's statement be correct, the proper cerebral termination of the optic nerve gains rapidly upon its sensorial roots in the ascending series of Mammalia, and is particularly developed in Man. And if he be further justified in the assertion, that the fibres of this cerebral root directly proceed to all parts of the surface of the hemispheres, but primarily and especially to the posterior, it seems to us that one of the chief foundations of Mr. Dunn's theory,—namely, the primordial nature of the great internal convolution,—is knocked away. The anatomical relations of what Mr. Dunn regards as the primitive convolutions to the superadded, do not at all correspond to our notion of their physiological connexion. For we should have expected that if there were any portion of the cerebrum set apart for the perceptive conciousness, it would have been a stratum of grey matter interposed between the sensorial centres and the convolutions, and not any portion of the periphery itself.
Again, it goes very much against our notions of cerebral action to suppose that any particular set of convolutions are the instruments of thought and reflection, as distinguished from simple ideation. Our whole mental life consists in a succession of ideas and of feelings connected with them; and that succession, the order of which is determined suggestively, seems to us much more related to the mode in which the different parts of the convoluted surface are connected with each other, than to the independent operation of any particular parts of them. We are by no means opposed to the notion that different parts of the convoluted surface may be instrumental in the formation of different classes of ideas (though we do not as yet see any valid evidence that they are so); but the linking-together of these ideas by associations of various kinds, on which depends the growth of our reasoning powers as well as of the imaginative and poetic faculty, can hardry be the work of a set of convolutions disconnected from the rest. Besides, the transverse convolutions, to which Mr. Dunn assigns this office, are already developed as fully as any other part of the hemispheric ganglia, in the brain of the infant; and yet its mental life for years to come is scarcely elevated to all appearance above that of the brutes. But during those years we believe that a store of perceptions and of simple ideas founded on them is being laid up; and that a development of commissural fibres is taking place,—partly according to an original plan, varying, like the shape of the brain itself, in each individual, and partly in accordance with the habitual mode in which the organ is used,—which fibres co-operate with the vesicular matter of the convolutions they connect, in establishing those peculiar relations between ideas, which determine their succession in the modes which we denominate Memory, Imasnnation, and the like.
In thus expressing our differences from Mr. t)unn, we must at the same time record our sense of the great value of his Essay, as one calculated to prove a stimulus to thought in others, and to direct intelligent minds to a field of inquiry
• Bee Article, Binocular Vision, in Edinburgh Review, Oct . 1868.
which can only he really productive when cultivated hy men of Mr. Dunn's powers of observation and reflection. The difficulties of the work are great; but that should not be a ground of discouragement, for difficulties were made to be overcome; and the example of Mr. Dunn is sufficient to show that a man who has at the same time the capacity and the inclination to do something for the promotion of scientific inquiry, will find means to do so even in the midst of the distracting cares of an active professional life. The more extensive his practice, indeed, the more sure he is to find something worthy of being noted and recorded; and we would point to the succession of cases which Mr. Dunn has published at various times, as among the most valuable contributions to this department of inquiry with which we are acquainted,—in regard alike to the mode in which their psychological and their pathological phenomena are recorded.
On Chloroform and other Anmsthetics; their Action and Administration. By John Snow, M.D., Licentiate of the Royal College of Physicians. Edited, with a Memoir of the Author, by Benjamin W. Richardson, M.D., Licentiate of the Royal College of Physicians.—London, 1858. pp.443.
A r Anic has lately seized the public mind in reference to the employment of chloroform,s because in rapid succession several deaths have occurred which appeared fairly attributable to this agent. If these deaths have proved anything, they have proved the truth of the observation of the earnest worker, now, alas, no more among us, that chloroform partakes of the character of all powerful agents in requiring to be used with care and with a due regard to the ordinary laws both of pneumatics and of vital dynamics. To judge by the remarks] that meet us on all sides, one would suppose that a grand discovery had just been made that anaesthesia was to be purchased only at the risk of life, and that medical men had hitherto been using chloroform, ether, or amylene at haphazard, rather perhaps with a view to saving themselves trouble, than for the purpose of relieving their patients of pain and suffering. But as medical men seized avidly upon the great suggestion of etherization, because they felt it to be one of the greatest boons that could be conferred upon mankind, and a certain means of advancing the science and art of medicine, so they also at once recognised the dangers which surrounded the employment of anaesthetics, and sought to determine the exact limits which should guide us in their administration. No one thinks of decrying railways because of the occasional accidents, however fearful, which are attributable to negligence in some quarter; nor is our steam fleet in danger of being abandoned, and emigration arrested, because terrific conflagrations or explosions prematurely hurry hundreds of men, women, and children into the arms of death, owing to culpable neglect of precautions which we all know to be necessary. Dr. Snow, more than any other physician, has assisted in promoting the use of anaesthetic agents after their first introduction into the practice of medicine; but no one more fully appreciated the dangers which may surround its employment, or sought more earnestly to prevent the occurrence of those lamentable issues which from time to time have startled us from our feeling of security. The numerous experiments so carefully conducted by Dr. Snow amply testify to the sound judgment-which he held upon these questions. He was not led away by enthusiasm to overlook the necessity of well weighing all the circumstances that influence the result produced by chloroform and its congeners; and his large experience at the operating-table and at the bed-side only served to stimulate this earnest student to ever renewed efforts, not only to lessen the risks attending the use of known anaesthetics, but also to discover others which might be exempt from the charge of endangering the patient, even if exhibited in a careless manner. He thought at one time that he had in amylene found a hydrocarbon which accomplished all he desired; but two deaths which occurred under his own administration bitterly disappointed these hopes: yet the energy and indomitable perseverance of the man would certainly have carried him on to ultimate and complete success had not the hand of death been laid upon him, and arrested a career which may well serve as an example and as a beacon. The interesting and warm-hearted memoir prefixed to Dr. Snow's work, by one whom we all know, tells us of no thrilling deeds and hairbreadth escapes, but it informs us how, by hard work and determination, Dr. Snow overcame the dragon that opposes the progress of so many a London physician, and had reached the tree from which the Golden Fleece was suspended; it reminds us how, as early as 1848, Dr. Snow saw the principles upon which the action of narcotic inhalations are based, and knew their dangel's commensurate with their power of doing good.
"He demonstrated that these substances modify, and in large quantities arrest, the animal functions, in the same way and by the same power as that by which they modify and arrest combustion; the slow oxidation of phosphorus and other kinds of oxidation unconnected with the living body when they (the narcotics) are mixed with the atmospheric air. .... Placing a taper during one of our experiments in a bottle through which chloroform vapour was diffused, and watching the declining flame, he once said, 'This, now, is all that occurs in narcotism; but to submit the candle to the action of the narcotic without extinguishing it altogether, you must neither expose it to much vapour at once, nor subject it to the vapour too long, and this is all you can provide against in subjecting a man to the same influence. I could illustrate all the meaning of this great practical discovery of narcotism on a farthing candle, but I fear the experiment would be thought rather too commonplace.'" (p. xvii.)
To those who have followed the medical literature of the last ten years, Dr. Snow's views will be known from the various papers which he has published in various periodicals, but especially* in the old Medical Gazette during the years 1848-1851. The present volume is, however, by no means a recftaufe; new experiments, and a careful summary of the very extensive experience which Dr. Snow has enjoyed in the use of chloroform, in surgery and medicine, since its first introduction into practice, are added, and the whole forms a work which ought to be read by all practitioners. They can nowhere find a more lucid account of very important inquiries into the physiological and therapeutic action of chloroform and some other anesthetics; and whatever the ultimate fate of chloroform may be, the labours of Dr. Snow will ever serve as a guide and pioneer to those who wish to extend and establish the benefits that accrue to suffering humanity through the removal of pain.
The book was, so to say, completed on the death-bed; the editor has only added the index and the memoir already alluded to; we have, therefore, as every page testifies, the bond fide production of the lamented Dr. Snow. After an historical introduction, and some general remarks on inhalation, the properties and preparation of chloroform, with its physiological effects, and the circumstances modifying those effects, are examined. Most medical men are familiar, from observation, with the various degrees of narcotism which the inhalation of chloroform is capable of producing; but we fear that even those who habitually employ it, or cause it to be employed, are unacquainted with the valuable experiments and calculations of Dr. Snow, made with a view to determining the exact ratio that exists between the quantity of vapour introduced into the circulation, and its anesthetizing effects. The experiments were made by introducing into glass jars, birds, guinea-pigs, cats, with definite quantities of chloroform; the cubic contents of the jar being ascertained, it was easy to calculate the exact amount of saturation of the contained air. By noting the time at which the different effects of the vapour became perceptible, and comparing the results thus obtained with one another, and with the data that we possess regarding the respiratory functions of man, Dr. Snow
has arrived at a series of conclusions which establish his character as an inductive philosopher. The book before us happens to be open at page 66. We quote the fifteenth experiment as an instance of the author's mode of procedure :—
"A cat was put into the jar holding 3000 cubic inches, and 82-5 grains of chloroform were introduced, being two grams and three-quarters to each hundred cubic inches. In five minutes it had evaporated, and the cat began to stagger in its walk. In two minutes more it was unable to stand. Five minutes after the chloroform had evaporated the cat was quite insensible, and breathmg one hundred and twenty-six times in a minute. It was now taken out. The temperature in the axilla was 98°. In half an hour after its removal from the jar it had recovered its consciousness, but was still drowsy.
"It was now put into the jar again, and the same quantity of chloroform was introduced in the same manner as before. In five minutes it had evaporated and the cat was again insensible. In other five minutes it was breathing rather deeply forty-eight times in the minute. Twelve minutes after the chloroform had evaporated, the cat was breathing in the same manner, but sixty-eight times in the minute. The breathing afterwards became shallow and feeble, and half an hour after the chloroform had evaporated it was eighty-eight in the minute. In five minutes more the breathing ceased. The cat was taken out of the jar, and the stethoscope was applied to the chest. The heart could not be heard to beat at first, but in a short time the cat gave a gasp, and the heart's action returned, and the breathing became re-established."
The conclusions which Dr. Snow draws from the experiments are probably known to our readers; but no harm can result from those which have an especial practical bearing being again put upon record. He shows that one grain of chloroform to each hundred cubic inches of air suffices in cats, guinea-pigs, and mice, to induce the second degree of narcotism, or that state in which consciousness and voluntary motion are nearly but not entirely abolished. Again, he finds that serum at 100°, and at the ordinary pressure of the atmosphere, dissolves about its own volume of vapour of chloroform; and he calculates that one part in 16,285 is the average proportion of chloroform by measure in the blood in the second degree of narcotism. Assuming the total amount of blood in the human adult to be, according to Valentine's calculations, about 30 pounds, he infers that twelve minims of chloroform is the quantity which must be received into the circulation to produce narcotism of the second degree. A larger amount is employed in practice, because so much is lost in the processes ordinarily used for inhalation; but Dr. Snow has found that by introducing twelve minims into a bladder, and causing the vapour to be inhaled over and over again, as is done with laughing gas, narcotism of the second degree is produced.
This is clearly one important fact not to be lost sight of in the administration of chloroform. The second and parallel one in its bearmg upon practice is the proved uecessity of avoiding the introduction of a large quantity of vapour suddenly into the circulation, in order to enable the system to accommodate itself to the new conditions under which it is placed. Although we feel assured that death may be induced by chloroform in various ways, there is ample evidence to prove that in the great majority of cases it results from the paralyzing influence which the vapour exercises upon the heart. In most of the fatal cases, the presence of a weak and more or less degenerated heart has facilitated this deleterious action; but Dr. Snow has proved to us that even in diseased conditions of the heart we need not fear the administration of chloroform by inhalation, provided we guard against the introduction of a disproportionate amount at once—provided we see that the air taken into the circulation is not charged with too much of the vapour of chloroform, especially at the commencement of the operation. It is manifest that it must be desirable to graduate the amount of chloroform vapour taken up by the air inhaled with as much exactitude as possible, and that it is impossible to do so if the chloroform be applied to the nostrils on a handkerchief, or on lint folded together. The most exact way, as might suggest itself from what has preceded, would be to introduce a measured quantity into a bag, and having filled it by means of bellows, to allow the patient to inhale it again and again. Dr. Snow tried this plan, and found that he obtained very uniform results; but although he regarded the plan as perfect so far as regarded the safety of the patient, he abandoned it on account of cer