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creased activity without any additional impulse being given to the circulation, bis doctrine may acquire plausibility, but such a phenomenon is at variance with every thing we know both in the animal and in the vegetable kingdoms. As well may we suppose that plants will grow better without than with water, and ihat the urine will be as copiously secreted from kidneys that are torpid as from these organs in a case of diabetes.

Mr Carmichael looks upon sleep as being occasioned purely by mechanical compression, or something so closely resembling it, that I must regard the two circumstances as identical, so far as the present argument is concerned. I am perfectly aware that such compression will occasion sleep; but this Í hold to be the sleep of disease, and not of health. Effusion of blood, of serum, or of purulent matter upon the brain,-a torpid state of the bloodvessels of this organ-or the beating in of a portion of the skull cap, --will throw the person into stupor or sleep, by paralyzing, with their pressure, the cerebral texture. Eating or drinking to excess, by inducing congestion approaching to apoplexy, will do the same; so will foul air or narcotics; but the pure sleep of health has no affinity to these adventitious conditions. So far from there being any increase of blood in the brain during healthy sleep, it is proved that the circulating Auid in that organ is actually lessened, as I have had occasion to shew in a case related by Blumenbach, of a person who had been trepanned, and whose brain was observed to sink when he was asleep, and swell out when he was awake. The abolition of the cerebral functions is, to my mind, sufficient evidence of diminished action going on in the brain. I cannot conceive increased assimilation without increased circulation, nor increased circulation without augmented functional energy. To admit the first without allowing the second, is to presume the existence of an effect without any corresponding cause.

Supposing, however, that healthy sleep is always occasioned by the mechanical compression, or similar cause, spoken of by Mr C., how are we to account for people being so easily awakened ? Sleep should be like apoplexy: it should be difficult or impossible to arouse a man till the pressure is removed.--Yet we constantly see people awakened from the most perfect sleep by very trifling causes. What, in such a case, becomes of this pressure? Is the load at once lifted off the person's brain? What becomes of the assimilative particles which are squeezing his senses out of him, and submerging him under the billows of sleep? It is as difficult to conceive that such mechanical pressure could be instantaneously removed, as that any deposit of new matter which ever takes place could have the effect of a foreign body acting upon the brain.

Dreaming is inconsistent with this gentleman's theory. AssiVOL. IX.-NO. XLII.

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milation is a general process; but, according to him, one part of the brain may be fattening while another is starving. It seems as rational to infer that the assimilative operation is at work in one leg, and at a stand in the other.

Mr C. endeavours to strengthen his case by the instances of General Elliot and Dr Reid, but these must be looked upon as idiosyncrasies. Generally speaking, the more sleep a man takes the less food can be do with; and a hard-working, active, lightsleeping man will require more food than a great dozer. Dr Reid seems to have acted on the principle of the boa constrictor. By over-eating himself, he induced a plethoric state of the brain, the mechanical compression upon which threw him into a torpor' similar to that which falls over the snaky monster of the wilderness, when gorged with food. His two days slumber was not the repose of health-not the sound sleep induced by the spontaneous and periodical exhaustion of nervous energy.

The theory of the nervous energy, or sensorial power, to which Mr C objects as not sufficiently definite and expressive, appears to 'me singularly adapted to explain the different phenomena of sleep. - I conceive this power to exist in a ratio corresponding to the activity of the circulation. In fever, phrenitis, or 'mental excitement of any kind, it is excessive, and the person remains awake. My view of the case is, that, to induce sleep, we have only to quell the action of the sensorial power--in other words; to relax the force or irritability of the vascular system : According to Mr C., it is necessary that the brain should be compressed by a physical agent operating upon it. This agent is the deposit of new particles, the result of increased activity in the assimilating vessels of the brain. Now, as such an increased action in these vessels cannot take place without augmented energy in the local circulation, it follows that the very eircum

, stances which, according to me, occasion wakefulness, according to him give rise to sleep... 11

Mr C. has, with no small ingenuity, endeavoured to shew that the facts stated by me, especially those with regard to the effect of food in inducing sleep, bear out his hypothesis; but on this point I think it will not be difficult to show that he labours under a mistake." I impute the soporific propensity of great eaters to the large quantity of food in the stomach draining the nervous energy of the brain, or inducing an apoplectic state : it may often act in both ways. I do not employ the sensorial power as a mere imaginary agent for the explanation of phenomena which cannot be easily accounted for without it; for Í hold its existence, and the way in which circumstances are modified by it, perfectly susceptible of demonstration. We can show that one organ may have an excess, and another a deficiency, with as much ease as that one body may be positively, and another negatively, electrified. There are particular times when certain organs require a larger share of sensorial power than at others, and when material injury is done if any violation is offered to this necessary law. After eating, for instance, it is perfectly well ascertained that digestion never proceeds so well as when we give ease to the brain, and do not employ it in study; while the digestive process is impaired by working the brain immediately after taking food. To what are these circumstances to be attributed, but to the law that when food is thrown upon the stomach this viscus digests better if it be supplied from some other source with additional nervous energy? For the same reason, exercise of any kind is bad shortly after eating, as the sensorial power not only of the brain but of the muscles is at work, and so much is thus lost to the parts concerned in digestion. These are not solitary facts: a hundred more might be brought in support of the point which is here contended for.

Circumstances, indeed, would rather induce as to infer, not only that increased assimilation in the brain is not the cause of sleep, but that the assimilative process is nevet so feeble in that viscus as when its functions are locked up in slumber. In this respect the brain differs from other organs; but the analogy between it and them is not, on that account, less complete, in so far as in all cases an organ is most liberally supplied with the .circulating fluid when the greatest efforts are demanded from it. The brain works in the waking state, and is then most highly vascularized-the stomach and liver labour hardest while we are asleep, and are consequently at that time most copiously excited with the stimulating nutriment of the circulation.

Active-minded, deep-thinking, or care-worn men have often, perhaps generally, a bad digestion. The stomach does not act well even when the appetite (a rare case) is unimpaired ; and they are in the habit of using medicines to stimulate the torpid action of the alimentary canal. They sleep ill-perhaps they lie half of the night before slumber visits their eyelids-perhaps the other halt is spent in dreams. Men of dull, easy, contented minds, are in every respect the reverse. They eat like horses, and think of nothing but the next meal. At night they lay their stupid heavy heads upon the pillow, and instantly fall into a profound slumber--a slumber unbroken even by the slightest glimpse of a dream. Why are not these men alike? Why does not the pale, thin, care-worn, deep thinker sleep as soundly as the sluggish obtuse glutton? Why does his sto. mach not perform its functions as kindly, and digest the food with the same ready alacrity? The cause is obvious. The brain of the first absorbs so much of the nervous energy of the stomach as not only to keep his mind active when it ought to be reposing, but to prevent the stomach from performing its functions with due vigour—and thus digestion suffers. The second thinks not at all. The sensorial power which kept his brain awake is transferred by an easy process to the stomach, which, reinforced in this manner, acts vigorously, and enables him to fatten upon its labours. The two organs are here re-acting upon each other ;-in the one case the brain starving the stomach, in the other the stomach starving the brain, and giving a practical vindication of the truth of the Shakspearian aphorism, that “ fat paunches make lean pates.”

The endless phenomena of dreams, “ for ever varying-never the same,” are easily and beautifully explained by means of the sensorial power. Partial assimilation (by which means alone can they be accounted for, according to the doctrine of Mr Carmichael) is a phenomenon unknown to nature in a state of health. We have no reason to suppose that particles are deposited in one part and not in another at the same time-none ihat such an operation is at work in this portion of the brain and not in that, its immediate neighbour.. Assimilation is a slow process, and cannot keep pace with the airy and fleeting character of visions, or account for their evanescent lights and shades. The nervous energy coming vividly into play in one organ while it is suspended in another, accounts readily and felicitously for dreams—their incongruities, rapid transitions, and other odd and miscellaneous features.

I shall conclude by mentioning one physiological fact, which, of itself, and without reference to any of the foregoing arguments, strikes with fatal effect at the theory of Mr Carmichael. The drowsiness that takes place shortly after eating, seldom lasts above an hour or two. This, Mr C. would say, arises from the brain being oppressed by the deposit within it of new particles, which must necessarily be derived from the food lately taken. Here we must suppose that assimilation commences immediately. Now, it is an admitted fact, that the preliminary step of chylification does not begin till the food quits the stomach and passes into the duodenum, and that about three hours generally elapse before this transfer is effected. As soon as the mass is fairly out of the stomach and lodged in the intestines, the lacteal vessels begin to act upon it, absorbing its nutriment in the form of chyle, and sending it, by means of the thoracic duct, into the left subclavian vein. The chyle here enters into combination with the blood, and it is from this general mass that the particles which constitute the substance of the body are formed. The formation of these is what is called assimilationa process which Mr C.'s theory leads us to infer commences immediately, and is brought to a conclusion before the food has really got out of the stomach, or the preparatory step of chylification begun. If a man, after eating, feels drowsy in consequence of his brain being compressed by the deposit of new particles of matter, this deposit and the accompanying drowsiness must be simultaneous, whereas we find that the latter precedes the former by several hours. How much more simple and easy is it to suppose that the nervous energy which keeps the brain awake is transferred to the stomach, and that so soon as the purposes of the latter are served, it returns to the brain, which it puts into a state of activity, and thus dispels the tendency to sleep.

There are some other points in Mr C.'s essay which I think could also be made the subject of criticism ; but the principal positions having been taken up, it is perhaps not necessary to dwell on minor details. I shall therefore conclude with expressing the great pleasure I have had in perusing that gentleman's pa per, which is written not only with great ability, but in a spirit of fairness, candour, and good feeling, that do him the greatest credit.

ROBERT MACNISH. 29. West GEORGE STREET,

GLASGOW.

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SIR,

DONCASTER, September 17. 1834. I should not trouble you with the following remarks, but am bound to do so in common justice to myself and others. In your Journal for June, my work on Mental Culture was reviewed, and other phrenologists beside myself consider the article characterised by a want of fairness and capdour. I was at Reading at the time, and felt annoyed at the direct implication of my moral character, viz. that I had misstated facts and doctrines," and also substituted Spurzheim's ideas for my own, charges which were not substantiated by a single proof. Hence it was that I penned the angry epistle which appeared in the Berkshire Chronicle; and I will admit, that, like all such warm productions, my language and assertions were too intemperate and, in some measure, call for an apology on my part to Mr Combe and Mr Simpson, particularly as I attributed the obnoxious article to either the one or the other of these gentlemen.

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