Imatges de pÓgina
PDF
EPUB

remarking, that the nerves sent off from ganglia have a very different appearance from those coming directly from the brain and spinal marrow. Recherches Physiques sur la Vie et la Mort, &c. par M. Bichat.

[ocr errors]

Among the opinions which have prevailed respecting the cause of the will having no power over the muscles of involuntary motion, one is, that its influence is intercepted by the ganglia. It appears, from the experiments related in this paper, that they do not intercept the influence, either of stimuli or sedatives applied to the nervous system. Dr Philip ascribes our having no power over these muscles to their obeying stimuli which we cannot influence, and to our not being conscious of their motions.

The author's next object is, to ascertain whether the power of the blood-vessels is as independent of the nervous system as that of the heart; and whether this system possesses over them the same kind of influence as over the heart. The experiments undertaken with this view were made on the capillaries of a frog.

·

<

It has been questioned,' he remarks, how far inferences, drawn from experiments made on cold-blooded animals, can be supposed to apply to those of warm blood. Both Fontana and Dr Monro ob serve, that, in their experiments, they found the system of both obeying the same laws. The experiments I have had occasion to lay before the Society tend to confirm this observation; and I may say the same of all the experiments I have made on both sets of animals. There are certain circumstances in which they evidently differ; in all others they seem to agree.'

In experiment 11th, the head was cut off, after a ligature had been thrown round the neck, to prevent loss of blood; and the spinal marrow was destroyed by a wire. On bringing the web of one of the hind-legs before the microscope, he found the circulation in it vigorous, which it continued to be for many minutes. Thus it appears that the blood-vessels retain their power after the nervous system is destroyed.

In order to ascertain whether the blood-vessels are capable of being directly stimulated through this system, it was, in the first place, necessary to ascertain whether the vessels can support the motion of the blood, independently of the heart. For this purpose, a ligature was thrown around all the vessels attached to the heart of a frog, and the heart cut out. The motion of the blood in the extremities was still found to be rapid.

Much difficulty occurred in attempting to proceed further. In order to ascertain the effect of stimuli applied to the nervus system on the vessels of the foot, it is not only necessary to

remove the heart, and lay open the cranium, but also to prevent the voluntary motions of the animal, by destroying its sensibility and power of voluntary motion. Dr Philip observes, that,

Notwithstanding this experiment was repeatedly performed with the greatest care, the circulation by all these preparatory means was so enfeebled, that, although the blood still moved in the web, it was in so irregular and uncertain a way, that I never could arrive at any positive conclusion respecting the effect of the stimulus applied to the brain. After many fruitless attempts, therefore, I abandoned this mode of making the experiment.

He therefore had recourse to the effects of sedatives. These, it is evident, will not be increased by the action of the muscles; and, as cutting out the heart does not immediately impair the circulation in the extremities, it is evident that any effect which the sedative may have on the heart may be overlooked. He thus, in experiments 14th and 15th, ascertained, that agents applied to the brain are capable of immediately influencing the vessels of the extremities.

It appears, from experiment 16th, that, analogous to what was observed of the heart, we cannot, either by chemical or mechanical agents, excite irregular action in the blood-vessels. Their action is only rendered more or less powerful. Dr Philip observes,

The irregular appearances in the circulation in the web of a frog's foot, mentioned by Dr Thomson, professor of military surgery in the University of Edinburgh, in his lectures on Inflammation, lately published, and which he ascribes to inflammation, may be observed in any case, if the vessels be at all compressed in applying the foot to the microscope; and, although they are not compressed, these appearances very generally occur when the circulation begins to fail. The blood will then stop and go on at intervals, and move backwards and forwards in the same vessel. I have often watched the capillaries, from the commencement of inflammation to its greatest height, when the part is about wholly to lose its vital power, in the mesentery of a rabbit, the web of a frog's foot, and the fins of fishes, without perceiving the least tendency to this irregular motion, when tlie part viewed was so applied to the microscope as not to compress its vessels.

From the 17th and 18th experiments, it appears, that the power of the blood-vessels, like that of the heart, is capable of

* An account of these experiments is published in the introduc tion to the second part of my Treatise on Febrile Diseases, and a plate given, representing the state of the vessels in the different stages of inflammation.

VOL. XII, NO, 45.

G

being destroyed through the medium of the nervous system. The vessels instantly lost their power on suddenly crushing either the brain or spinal marrow.

From all the experiments and observations in this paper, Dr Philip draws the following conclusions

1. That the laws which regulate the effects of stimuli applied to the nervous system, on the muscles of voluntary and those of involuntary motion, are different.

2. That both mechanical and chemical stimuli, applied to any considerable portion of the nervous system, increase the action of the heart.

6

3. That neither mechanical nor chemical stimuli, applied to the nervous system, excite the muscles of voluntary motion, unless they are applied near to the origin of the nerves and spinal marrow.

4. That mechanical stimuli, applied to the nervous system, are better fitted to excite the muscles of voluntary motion, and chemical stimuli those of involuntary motion.

6

5. That, after all stimuli applied to the nervous system fail to excite the muscles of voluntary motion, both mechanical and chemical stimuli, so applied, still excite the heart.

6. That both mechanical and chemical stimuli, applied to the nervous system, excite irregular action in the muscles of voluntary

motion.

7. That neither excite irregular action in the heart, nor is its action rendered irregular by sedatives, unless a blow which crushes the brain be regarded as a sedative.

"

8. That the excitement of the muscles of voluntary motion takes place chiefly at the moment at which the stimulus is applied to the nervous system:-that of the heart continues as long as the stimulus is applied.

9. That the muscles of voluntary motion are excited by stimuli applied to very minute portions of the nervous system.

10. That no stimulus applied to any minute part of the nervous system can excite the heart.

11. That the heart obeys a much less powerful stimulus, than the muscles of voluntary motion.

12. That the facts expressed in the three last sentences, 9, 10, 11, afford an easy explanation of those expressed in the preceding

sentences.

13. That the power of the blood-vessels, like that of the heart, is independent of the nervous system.

14. That the blood-vessels can support the motion of the blood after the heart is removed.

15. That the blood-vessels are directly influenced through the nervous system in the same way that the heart is.

(

16. That, analogous to what we observe in the heart, no stimu lus or sedative applied to the nervous system excites irregular action in the blood-vessels.

17. That the power of the blood-vessels, like that of the heart, may be destroyed through the nervous system.

18. That the office of the ganglia is to combine the influence of the various parts of the nervous system, from which they receive nerves, and to send off nerves endowed with the combined influence of those parts.

19. That the will has no influence over the muscles of involuntary motion, because, in their ordinary action, they obey stimuli over which we have no influence, and because at all times we neither see nor are otherwise conscious of their motions, and consequently cannot direct them.

20. That we have reason to believe that the division of the encephalon into the cerebrum and cerebellum, relates to the sensorial functions, since it does not appear to relate to the nervous functions; the muscles of voluntary and those of involuntary motion being influenced in the same way by both.

21. That the sedative effect is not the consequence of previous excitement, but the effect of a certain class of agents.'

III.

Commentaries on some of the most important Diseases of Children. By JOHN CLARKE, Esq. M. D. &c. &c. &c. Part the First, 8vo. pp. 198. London, 1815. Longman & Co.

THIS title-page, we suppose, was partly the composition of the author, and partly of the booksellers; the left-handed compliment of attaching esquire and three unmeaning et cæteras to the name, probably emanating from the latter, according to the notions of precedency and dignity in Paternoster-row. We sincerely lament that the author should have survived for so short a period the publication of this volume, (which appears to be but the first part of a series of commentaries), at a time of life when the vigour of his intellect, and the comparative leisure in which he had begun to indulge, might have been expected to afford him the power, as he had evinced the inclination, of laying open the stores of his long and ample experience in this department of practice. We know not whether he had made any progress in the composition of the subsequent parts of this work; but from the desultory manner in which this is confessedly written, and from the little art or labour apparently employed in the arrangement of the materials, we should be disposed to think that the author had related the chief results of

his personal observation currente calamo, and sent them to the press before he had made much further progress in the work. We mention not this in disparagement to the execution of the work, which has probably gained in spirit what it may have lost in formality and method.

In the first chapter, the author has given some interesting ⚫ general observations on the diseases and mortality of children, and on the state of medical knowledge on these points.' After pointing out the inaccuracy of the bills of mortality, especially in respect to the births, and suggesting some means of improvement, he shows, that of all the children born within the district of the bills, nearly one-fourth die under two years of age, and of the survivers about a fifth under ten. In some years the proportion is much larger. Alluding to the speculations of Malthus, he remarks, that the want of subsistence in this country cannot be a sufficient cause for this extensive mortality at those periods of life, and that it is, doubtless, attributable to some mismanagement of young children. He justly condemns the mischievous practice of attempting to harden them by scanty clothing and exposure to cold, to which he ascribes not only much early disease, but the occurrence of scrofulous and phthisical complaints in more advanced life: and he refutes the appeal to the experience of the poor, by affirming, that a large proportion of the mortality of children occurs in the families of the poor, who rear comparatively few, in consequence of the morbid influence of cold, bad air, uncleanliness, crowded apartments, neglect, and the constant prevalence of contagions in large towns. He descants at some length and with considerable feeling on the necessity of some legislative interference to prevent the artificial propagation of these contagions, and suggests the means of accomplishing it; passing, by the way, a warm and well-merited eulogium on the character and conduct of Dr Jenner, the benefactor of mankind. In addition to these sources of infantile disease, children are liable to other causes of disorder peculiar to their time of life, of the nature of which physicians were kept in ignorance down to a very late period, in consequence of the exclusive employment of women in the practice of midwifery, many of whom merited the character given by Terence. Sane pol! ista temulenta est mulier et temeraria. This leads the author to a brief historical sketch of the rise and progress of scientific midwifery in this country, and of the series of medical writings on the diseases of children, down to the works of Dr Hamilton and Dr Burns, which he highly commends. The talents and high character of Dr William Hunter, gave the first importance and respectability to the practice of midwifery, which had been deemed disreputable, and a

« AnteriorContinua »