THE ſubject of SLEEP, like many other ſubjects in medicine, cannot be reduced to the principles of mathematical certainty; but, that it may be illuſtrated by a complete induction of the effects of all the exciting powers producing ſleep, I imagine, will not be denied.

"SLEEP, without dreaming," ſays Mr. Locke, is reſt from all ſtudyOn the Human Underſtanding. of the mind and operation of the animal functions of the body. In "ſleep", when "quite complete," ſays Dr. Cullen, the motion and mobility of the nervous power, with reſpect to the whole of what are called the animal functions, entirely ceaſe; or, as I would expreſs it, are in a ſtate of collapſe, and are very different from the ſtate of waking, which, in healthy perſons, I would call a ſtate of general and entire excitementFirſt Lines of the Practice of Phyſic, vol. iv. pag. 127.. That there is a certain degree of excitement, neceſſarily exiſting in the animal ſyſtem, to conſtitute perfect and uninterrupted health, is agreed on by all. There muſt alſo be, I conceive, a certain point, or degree, of excitement, different from the foregoing, favouring profound ſleep, which is produced by certain powers operating on the living property inherent in every animal. This property has received different names, from different authors. It is called by Baron Haller the vis inſita; by Dr. Cullen, the nervous power; by Mr. John Hunter, ſtimulability; and by Dr. Brown, the excitability. The exciting powers acting on the excitability, producing excitement favourable to health, and inviting ſleep, if carried beyond their proper boundaries, or withheld, occaſion morbid ſleep, diſeaſe, and even death itſelf. The ſleep-inviting point, or that degree of excitement neceſſary to conſtitute profound ſleep, appears to exiſt in a kind of indirect debility of the ſyſtem, or partially-exhauſted excitability to the powers producing it, which it is very difficult to explain. Sleep, then, is the effect of the actions of the day, at firſt always giving more and more excitement, but leſs and leſs in proportion to the continuance of their operation, but in ſuch a ſort as always to add ſome excitement, till at laſt the matter comes to a point, where the degree of excitement neceſſary to conſtitute the waking ſtate no longer exiſts. Every day's experience teaches us the effects of the exciting powers, in producing ſleep: It teaches us, that, if they are applied in exceſs, or, though moderate, are long continued, they run the excitement on to actual indirect debility, and occaſion morbid ſleep. And, that ſleep may be brought on ſooner or later, by the exceſſive or deficient application of the cauſes producing it, is certain. By all unuſual exertions, thoſe unaccuſtomed to fatigue, &c. will have their ſleep hurried or produced ſooner than in common, and it is generally of the morbid kind.

A MAN of ſcience and of genius, in the purſuit of mental acquirement, ſtimulated by the ſpirit of emulation, or any other exciting emotion, will have his excitability conſiderably waſted, and his excitement increaſed beyond the point conſtituting profound ſleep, but favouring the waking ſtate; and this ſtate may be kept up, or rendered more tolerable, a conſiderable time, by the aſſiſtance of the diffuſible, together with the durable, ſtimuli, given at proper intervals, and changed frequently in kind, and in quantity, and accommodated to the excitability then exiſting in the ſyſtem, favouring the waking ſtateSee Dr. Brown's Elements of Medicine, in note of § xxxi,.

I THINK it has been ſufficiently proven, that the cauſes producing profound ſleep, or ſleep without dreaming, deprive the mind of reflex-ſenſation. Mr. Locke (on the Human Underſtanding, in the firſt volume) obſerves, that the ſoul does not think during profound ſleep, and that this cannot be proven, as there appears to have been a ſuſpenſion of time to the ſleeping man. The Chevalier Ramſay obſerves, It is falſe to maintain, with the Carteſians, that the ſoul thinks always. They never did, nor can, give any ſolid reaſon for this aſſertion. Experience ſhows the contrary, when we are in a ſwoon, or in deep ſleep. To think, know, and feel always, are privileges of a pure and unfallen ſtate, when the living images ſhall have a perfect reſemblance to him who never ſlumbers. This is one of the principal changes made in nature ſince the fall, and a law eſtabliſhed in the ſphere of lapſed ſouls.

THE reaſon why children ſleep ſo much, has been ſuppoſed, by ſome, to be owing to their wanting reflex-ſenſation. May not the phaenomenon of ſleep in children be explained upon other phyſical cauſes, and not upon the want of reflex-ſenſation? That the excitability of a child is more abundant, cannot, or will not, I imagine, be denied; and from this I may juſtly infer, that the waking and ſleeping ſtates of children do more eaſily run into each other than they do in adults. Their excitability, therefore, is more ſuſceptible of the action of ſtimuli of every kind, and the ſleep-inviting point is, conſequently, produced, or brought on, ſooner in children, by fewer cauſes, in a given time, than in adults.

A PATIENT in a convaleſcent ſtate of a typhus-fever is conſiderably debilitated, and very excitable to any ſtimulus over-proportioned to the abundant excitability then exiſting in the ſyſtem. The point at which ſleep begins is ſooner produced by ſtimulant powers, and the waking ſtate is likewiſe ſooner brought back; the intervals between the two ſtages of ſleeping and waking are of leſs duration, and ſleep is leſs profound than in a ſtate of perfect and uninterrupted healthThis idea may be extended to the female ſex, as their original ſtamina, and the life they purſue, render them more delicate, and, of conſequence, their excitability more abundant, than in the male. If theſe reaſons be admitted as phyſically true, which, I think, will be readily agreed to, it will help to enforce the validity of the aſſertion, that the intellectual faculties of the female are more ſuſceptible to impreſſions, their imagination more lively than that of the male; and the reaſon why there are more wits among the former than among the latter..

THE ſudden tranſition from ſleeping to waking, and vice verſa, is more obſervable in ſome perſons, under certain circumſtances, than in others; and theſe ſudden changes may apply to the above-mentioned caſes. It has been obſerved in other perſons, that the approach of ſleeping and of waking is more gradual, and, in theſe caſes, the ears are often awake before the eyes are opened, or ſee clearly, and the ſenſes are often awake before the power of voluntary motion is recovered. From the theory of ſleep which I have endeavoured to eſtabliſh, may not theſe facts be reſolved upon the ſame phyſical cauſes partially influencing the ſyſtem, and producing an unequal excitement and morbid ſleep?

IN a typhus mitior, the patient ſleeps much, with a kind of ſtertorous breathing, and is eaſily wakened by an addreſs not louder than common; withholding it, he ſoon falls into an involuntary ſleep. This kind of ſleep, for the moſt part, is the conſequence of a certain degree of debility, produced by ſome powers acting with conſiderable ſtimulant effect; the reaſon is, this ſleep depends upon leſs debility than that which conſtitutes the diſeaſe. How does it come about, that every thing which ſtimulates produces that effect by its ſtimulant, and not by its ſedative, virtue? Let thoſe accuſtomed to all the cauſes producing the ſleep-inviting point, be removed from theſe cauſes, and expoſed to the directly-debilitating powers, as darkneſs, ſilence, cold, reſt, and abſtinence; theſe cauſes leſſening the excitement (and accumulating the excitability), will increaſe a diſpoſition to involuntary morbid ſleep.

THERE are many facts which may be adduced in proof of this point. Even daily obſervation furniſhes us with arguments in ſupport of the poſition. Let us turn our attention to the induſtrious labourer, who is fatigued from his daily purſuits, expoſed to the ſtimulating rays of light, and the noiſe of the buſy world, who eats and drinks his hard earnings with a good appetite, and lays down to reſt, attended with profound, refreſhing ſleep. Dr. Zimmerman ſays, the ſoldier ſleeps even amidſt the thunder of the cannon, when he is worn out with exceſſive fatigueA Treatiſe on Experience in Phyſic, vol. ii..—Change the order; give him a day's reſt, ſilence, darkneſs, &c. and he will fall into ſleep of the morbid, reſtleſs kind.

THE regular returning time of ſleeping and waking, is to be explained upon principles ſimilar to the foregoing, and not upon the effects of habit. Habit is the effect of cauſes producing ſleep, and not the cauſe of ſleep; which is too obvious to need any further explanation.

FROM what has already been ſaid, we may explain the reaſon why all ſimple ſounds, as the ſound of a gentle caſcade, the beating of rain upon a houſe, vocal or inſtrumental muſic, induce a diſpoſition to ſleep. They are to be reſolved, likewiſe, upon the ſame phyſical principles as all other ſtimuli, producing partial exhauſtion of the excitability, and favouring th • ſleep-inviting point, and not upon the effects of ſound ſimply preventing reflex-ſenſation, and cauſing ſleep.—Sound and uninterrupted ſleep refreſh the bodily and mental powers, by accumulating, or bringing back, the greatly-waſted excitability to the ſtimuli of the preceding day, and preparing, or fitting it, for the operation of the exciting powers of the ſucceeding day.

IN the latter part of night, and towards morning, the excitement is conſiderably diminiſhed, the body in ſome degree weakened, and more eaſily affected by any ſtimulus, or hurtful power, that may be applied.

THIS living principle, inherent in the world of animals, upon which all natural ſtimuli exert their effects, in ſupporting the living exiſtence, is not confined to them alone, but is likewiſe extended to the vegetable kingdom. The greateſt phyſiologiſtBaron Haller. the world has hitherto produced, did not, indeed, admit of irritability in vegetables; but the induſtry and ſagacity of the Botaniſts have ſhewn us, that there is a very conſiderable number of vegetables, which exhibit ſigns of irritability, more or leſs obvious in proportion to their age, to their ſtrength, or to the part to which the irritating cauſe is applied. This has been obſerved in the leaves and flowers of ſeveral plants. Mr. Bonnet, of Geneva, has, I think, inconteſtibly demonſtrated, that the leaves of vegetables poſſeſs the power of voluntary motion. He has ſhewn us that theſe parts, or organs, always preſent their upper ſurface to the air, and that whenever a branch is turned out of its natural poſition, the leaves of that branch immediately aſſume a new direction. May we not venture to add, that the voluntary and involuntary motions of plants are more conſpicuous, and remarkable in the organs of fructification, eſpecially in the ſtamina and piſtils, than in the leaves, or any other parts, of vegetables; for in many plants, as ſoon as theſe generative organs have arrived at maturity, the ſtamina embrace the piſtil, with a ſeemingly-venereal appetite, and diſcharge their fecundating influence, from the cells of the antherae, upon the female organ—after this the ſtamina reſume their former poſition, and, in a ſhort time, pine, wither, and die? The involuntary and voluntary motions of vegetables, are obſervable in the Berberis vulgaris, or common berberry, and many others; the filaments of theſe plants, when touched by a pin, or any other mechanical ſtimulus, are immediately put in motion, and apply themſelves to the piſtillum, on which they diſcharge a portion of their fertilizing duſt. The wonderful irritability of the ſtamina of the Ciſtus Helianthemum The Dwarf Ciſtns, or Little Sun-Flower., is remarkable, chiefly, about ſun riſe; in the evening the irritability is nearly extinguiſhed, and on the following morning, this great, unequivocal, never-failing characteriſtic of life, returns again, and ſo on through the whole courſe of the vegetable life. All vegetables are more irritable in the morning than in the evening, to any ſtimuli that may be applied. The leaves of many vegetables, in the day, aſſume an appearance very different, from that which they do at night time. They are folded up, or contracted in the night; but in the day time, they are generally expanded; and, hence ariſes that particular ſtate of vegetables, which conſtitutes what Linnaeus and other naturaliſts have denominated Somnus Plantarum, or the ſleep of plants. During the continuance of this vegetable-ſleep, the appearance of the plant is ſo much changed, that the moſt experienced botaniſt is ſometimes at a loſs to know it, without a very minute examination. In ſome plants, the inviting ſleeping point may be induced by robbing them of light for a time, but upon the return of light, they reſume their waking ſtate. We may lay it down as a pretty conſtant and certain axiom, that the ſleep of vegetables, is more or leſs profound in proportion to their vigour or debility.Some of theſe hints on the irritability, voluntary and involuntary motions of vegetables, were ſuggeſted to me by Benjamin Smith Barton, M. D. Profeſſor of Natural Hiſtory and Botany in the college of Philadelphia, &c. &c.

IF the vigour and debility depend upon the effects of ſtimuli acting on the irritability in vegetables: If the motions likewiſe depend upon, and are ſubſervient to a "vegetable will;" and if ſleep more or leſs profound, depends upon the application of ſtimuli, which, I think has been ſufficiently proven; would it be unphiloſophical to infer, that vegetables, in time of morbid ſleep, are diſturbed with dreams peculiar to themſelves?

THE connection of cauſes and effects, traced in the vegetable world, and compared with thoſe of the animal kingdom, point out the ſtriking analogy between the two; and proclaim that Nature is uniformly the ſame in all her operations.

AN accurate knowledge of the effects of ſleep, upon the human ſyſtem, will enable us to ſee the propriety of fortifying the body, in the morning, with either the durable or diffuſible ſtimuli, againſt the noxious quality of the air at certain ſeaſons of the year; it likewiſe will further enable us, to point out the impropriety of the conjugal pair gratifying or indulging the hymeneal pleaſures in the morning. Thus, the temperature and purity of the air, food and drink, labour of body or of mind, the ſtimulus of light and ſound, the exerciſe of paſſion and emotion, when their ſtimulus neither ſtops ſhort of the proper point, nor goes beyond it, all give a diſpoſition to ſleep, of the moſt ſalutary kind.

BEFORE I conclude the ſubject of ſleep, I beg leave to mention a few remarkable, important, and valuable facts, concerning the Hybernation of animals, which will, beyond all ſcruple, help to reſolve many phoenomena in nature, ſhew the great ſedative power of cold, and the effects it has in producing ſleep, in many families of the animal kingdom. By the term Hybernation, is to be underſtood, that dormant ſtate in which animals of many different kinds, ſubſiſt in winter without food, without any apparent motion, and without ſenſe, ſeemingly ſound aſleep, and not recoverable from it unleſs placed in a warmer atmoſphere. It is to be obſerved, that this faculty is confined to thoſe animals that are the inhabitants of the colder regions of the earth; at leaſt we know of no inſtance of Hybernation of animals, which dwell in the intratropical parts of the earth. This ſtate of torpidity is moſt remarkable in the amphibious animals, ſuch as the frogs, the toads, the lizards, and, I ſuſpect, the ſerpents. There are likewiſe ſeveral quadrupeds, which are remarkable for remaining during winter in a torpid ſtate, ſuch as the bear, the badger, the ſquirrel, the hedge-hog, the dormouſe, the bat, &c. The Count de Buffon, and ſeveral other naturaliſts, aſcribe this ſtate to the coldneſs of their blood; but, according to Mr. John Hunter's experiments, it does not appear that the blood of the bear, of the hedge-hog, of the badger, or of the dormouſe, is a degree colder, than what we find to be in general the caſe, in animals of the ſame claſs. It has been found by experiments made by Mr. Hunter, that a frog receives and digeſts food, when it is in an atmoſphere in which the thermometer ſtands at 60°. but that it does not digeſt food when the cold comes down to 40°. It has from thence been ſuppoſed, that thoſe dormant quadrupeds, the bear, the badger, the hedge-hog, the dormouſe, and perhaps the ſquirrel, when the heat of their blood is reduced from 90°. and 100°. by cold to 70°. that then they loſe the power of digeſtion, and that the excretions, as well as the ſecretions, are very much diminiſhed. This is the moſt plauſible explanation of the fact hitherto offered.

DOCTOR Pallas ſays, the fuſlik becomes torpid in a great degree of cold; and that the heat of this animal is reduced from 103 to 80 of the ſcale of Fahrenheit.See Nova Commentaria Academiae Petropolitanae, • om. xiv.—In the hamſter, Sulzer has ſhewn us, that, during the ſummer ſeaſon, the pulſe beats one hundred and fifty ſtrokes in a minute; but that, if the animal is examined in the winter months, when in its torpid ſtate, the heart hardly pulſates fifty times in a minuteNatur • eſch▪ des Hamſters, pag. 16 • .. This laſt obſervation does not apply merely to the hamſter, but, I believe, it may be aſſumed as a fact, that, during the torpid ſtate of all hybernating animals, the pulſation of the heart is very ſlow. This remarkably-ſedative power of cold is not confined ſolely to the inferior animals: the influence of a cold climate on the human pulſe is prodigious. It has been found, for inſtance, that the heart of the Greenlander does not beat more than thirty, or forty, ſtrokes in a minuteBlumenbachii Inſtitutiones Phyſiologicae, p. 78. ſect. de Corde..

FROM comparing theſe facts and experiments, and the fifth and ſixth experiments of William Hewſon's Inquiry into the properties of the blood, may we not venture to draw the following concluſions? 1ſt. That cold is a great debilitating or ſedative power: 2d. That if the blood of ſome of the hybernating animals be actually at reſt for a conſiderable length of time, it may be rendered fluid by the gradual introduction of heat, and the animal reſtored to life. With theſe facts and obſervations, I finiſh the ſubject of ſleep, and now proceed, in the ſecond place, to the inquiry of Dreams.

FROM the theory of ſleep already given, I am enabled to proſecute with more propriety the ſubject of Dreams. It has been made to appear, that profound ſleep depends upon cauſes producing a certain degree of excitement favourable to the point at which ſleep commences, and that dreams are the effects of morbid ſleep, which depend upon the ſame ſtimulus either ſtopping ſhort of the proper point, or going beyond it. It is in this ſtate of ſleep, that the ſoul does think (according to Mr. Locke), when the intellectual functions are partially ſuſpended. Dreams may be explained, likewiſe, upon the ſame method of reaſoning, as ſleep. Certain powers do exert their effects on the principle of life, and produce an excitement unfavourable to refreſhing ſleep, which will be ſtrictly attended to in the courſe of this ſubject; and, I think, the old adage of philoſophers, will apply equally well here, as in many other caſes, "that Nature does nothing in vain."

I PRESUME, from what has been advanced, it will obviouſly appear, that a complete excitement of the brain, does neceſſarily take place in time of profound ſleep, different from that excitement, which takes place, in order to the proper exerciſe of the intellectual functions in the waking ſtate, and that, in time of morbid ſleep, there is either a deficiency or an exceſs of excitement, with reſpect to the different functions, in different degrees. In ſuch an intermediate ſtate of deficiency or exceſs of excitement in the brain, there always occurs more or leſs of dreaming: There are, in this ſtate, falſe perceptions, falſe aſſociations, falſe judgments, and diſproportionate emotions. In ſhort, the circumſtances attending dreaming, are obſerved to take place in delirium, only differing in degree.

IN ſthenic and aſthenic diſeaſes, when attended with delirium, the excitement in the former is carried beyond that point at which inviting ſleep commences, and, in the latter, ſtops ſhort of it.

THUS, I conceive, it will evidently appear, that there are two kinds of delirium, depending upon different degrees of excitement: the one is owing to an exceſſive, and the other to a deficient, degree of excitement in the brain. Further, it may, perhaps, ſerve to illuſtrate the analogy between dreaming and delirium; and the latter is only a bridge for the former to travel over to Inſania, if I may be allowed the expreſſion.

DREAMS affect thoſe moſt, who are of a debilitated and delicate habit, and thoſe eaſily affected by ſlight and trifling cauſes. A labouring man ſeldom dreams much. The ſleep of a labouring man in ſweet, whether he eats little or much, but the abundance of the rich will not ſuffer him to ſleepEccleſiaſtes, chap. v. ver. 12. . Beſides theſe, there are ſome healthy perſons who ſeldom or never dream at all. Mr. Locke tells us, he once knew a man that was bred a ſcholar, and had no bad memory, who told him, he had never dreamed in his life, till he had that fever he was then newly recovered of, which was about the five or ſix and twentieth year of his age. And, as a farther corroborating circumſtance, I have been informed by a gentleman of my acquaintance, that Dr. William Pitt Smith, of New-York, was acquainted with a lady of that city, who, at the age of twenty-three years, declared, ſhe had never dreamed in her life, and further, that the idea of dreaming appeared ſo abſurd to her, that ſhe did not believe there were any ſuch things as dreams.—I have no doubt, the world affords many more ſuch inſtances.

THE dreams of ſleeping men are, as I take it, all made up of the waking man's ideas, though, for the moſt part, oddly put togetherLocke on the Human Underſtanding, vol. i. pag. 76. ſect. 17. . That this is not always the caſe, may, I preſume, be proven upon Mr. Locke's own principles of reaſoning, that if all our ideas are derived from ſenſation and reflexion, which he endeavours to maintain, and if, in time of profound ſleep, the ſoul does not think, then dreaming moſt unqueſtionably muſt be, in time of morbid ſleep, when the powers of the mind are only partially ſuſpended; therefore, at that time, the organs of ſenſe are excitable to new impreſſions from cauſes ſuggeſted from without, and certainly they may beget new ideas within, and likewiſe excite thoſe into action already fixed in the mind, though, for the moſt part, incoherent.

It has been obſerved, in the former part of this diſſertation, that the excitability is more abundant in the latter part of night, and towards morning, than in the fore part of the evening, conſequently more eaſily affected by any ſtimuli, that may be at that time applied. This will, perhaps, enable us to explain more ſatisfactorily the phaenomenon of dreaming, at the approach of day, than at any period of the night; for it is generally remarked, that thieves make choice of what is vulgarly called the dead hour of the night, to make their depredations, when people are ſuppoſed to be faſt locked in the arms of profound ſleep.

FURTHER, in ſupport of this ſubject, I beg leave to adduce the following fact, from Dr. Beattie's Diſſertations Moral and Critical. He obſerves, that particular dreams might be accounted for from impreſſions made in time of ſleep on the organs of ſenſe, particularly thoſe of touch and feeling. A very ſlight hint, ſuggeſted from without, or in any way ſuggeſted, is ſufficient for fancy to work upon, in producing multitudes of viſionary exhibitions. I have heard from good authority, of a gentleman in the army, whoſe imagination was ſo eaſily affected in ſleep with impreſſions made on the outward ſenſes, that his companions, by ſpeaking ſoftly in his ear, could cauſe him to dream of what they pleaſed: once, in particular, they made him go through the whole procedure of a duel, from the beginning of the quarrel to the firing of a piſtol, which they put in his hand for • hat purpoſe, and which, by the exploſion, awaked him. I take the liberty of mentioning another fact, which will help to illuſtrate the very point in queſtion. It is a fact I obtained of a gentleman of my acquaintance, of extenſive obſervation and unblemiſhed moral character, who related his dream in the following words. I imagined I ſaw, at ten o'clock in the morning, a moon in the eaſt, ſhoot from itſelf like one meteor from another, fall to the horizon, and aſſume the appearance of a riſing full moon. Upon the appearance of this ſingular phaenomenon, I thought my dog ſtarted in purſuit of it. Immediately my imagination was changed to the weſt, where I fancied I ſaw a perſon deſcending from heaven, in a flame of fire. When it came in contact with the earth, a very great ſmoke iſſued, which ſeemed to ſpread far and wide. This was ſoon diſſipated, and I thought my companions ſaid they obſerved a man, who had deſcended in that flame of fire. They went off to meet him, and, behold, returned with a perſon dreſſed in a ſailor's grab: I aſked him from whence he came? he anſwered, he was taken up in a water ſpout, in a river (where he was fiſhing for his living) about ſixty miles from this ſpot; and he obſerved further, that he ſhould have deſcended much faſter, if it had not been for a large windlaſs he had hold of in his paſſage from above. A complete and judicious induction of the effects of theſe facts, are ſufficient to prove the aſtoniſhing vivacity of the imagination, the abſurdity and incoherence of the ideas in time of dreaming, and that they are not always made up of the waking man's thoughts.

I SHALL, in the third place, proceed to animadvert upon the effects of dreams on the faculties of the mind.

DOES not the exceſſive or deficient degree of excitement, conſtituting the morbid ſtate of ſleep, wherein certain faculties of the mind are awakened, ſeem to argue in favour of the different powers of the mind occupying different parts of ſpace in the brain? If ſo, it will help to reſolve the cauſes, why, ſometimes the imagination, the memory, and the judgment, are partially excited, and ſometimes deranged and impaired in dreams, and in diſeaſes. There are numberleſs facts that may be adduced, in proof of the effects of diſeaſes and accidents, in deſtroying, or impairing, the intellectual faculties. But, this is rather foreign to the preſent inquiry. I ſhall, therefore, confine myſelf to the effects of dreams on the faculties of the mind.

"THE imagination, or fancy, ſeems to be" one of all our mental powers, or faculties, the leaſt ſuſpended in its operation by ſleep. Of the other powers, or faculties, ſome are more, others leſs, affected, and ſome appear to be, for a time, wholly ſuſpended. That the memory is at times impaired or partially excited in ſleep, may be proven from this, that a perſon will dream of tranſacting buſineſs with a deceaſed friend, without recollecting any thing of his death. The judgment is frequently impaired in dreams, as well as in diſeaſes, and the imagination retains its vigour in tolerable force. That there is ſometimes an aſſociation of ideas in ſleep, I preſume, will not be diſputed; and it may be made to appear from this, that, if I dream of the object of my affection, it tranſports my imagination back to the place where ſhe moſt commonly reſides; but, for the moſt part, the aſſociation of ideas is falſe and deluſive, in our dreaming moments. Sometimes, the underſtanding is ſo deranged, and has ſo forſaken us, that we are entirely deprived of the power and freedom of the will. Hence, in dreams, we ſeem to experience a falſe neceſſity of running into trouble, pain, and many other perplexities, though, with a vigorous exertion of that power of the underſtanding, the will, we ſhould find a remedy or an antidote to all ſuch harraſſing ideas.

BUT ſleep has a wonderful power over all our faculties, beſides thoſe mentioned above. Sometimes ſuch a change takes place in the ſtate of the brain, from the influence of certain powers, that we ſeem to have entirely loſt our moral faculty. Hence, we ſometimes dream of perpetrating crimes without ſcruple or remorſe; crimes, both repugnant to law and to goſpel, and at which we ſhould ſhudder when awake. Would it be admitted, if I were to aſcribe this to the deſertion of the judgment?

AN attempt to explain all the dreams recorded in the Old and New Teſtament, upon the ſame phyſical cauſes as we do thoſe of the preſent day, would, perhaps, ſuggeſt a hint favourable to deiſtical principles, throw ſome objections in the way, and have a tendency to overturn, and retard the progreſs of, the Chriſtian religion, with ſome weak and wavering minds. Far be it from me, however, that I ſhould entertain, or even wiſh to ſupport, an idea, ſo unfriendly to the moral ſcience, to the happineſs, and to the good order, of ſociety: For we are warranted by the ſame ſacred hiſtory to believe, that dreams have given information of future events, and that they were revealed to ſome perſons, for certain purpoſes, by the Deity. Hence, weak and ignorant people infer, that they are ſtill prophetical, and ominous of their future events; but, what can be more abſurd than ſuch ſuperſtitious notions? Superſtition is one of the worſt diſeaſes of the ſoul. It is generally unfriendly to happineſs, to rational piety, and to ſound philoſophySee Dr. Beattie's Diſſertations Moral and Critical. . Then, as nature has done nothing in vain, may I not infer, that dreams are frequently of ſervice to ſome people? for, according to the Chevalier Ramſay, the Deity inſtitutted phyſical evil for the eradication of moral evil. May not, then, bodily and mental pain, which are frequently experienced in dreams, be of uſe to thoſe perſons in the way of phyſical admonition, and that they may be ſerviceable as means of moral improvement? For we find that bodily and mental pains were the remedies, employed in the Old Teſtament, for extirpating vice and promoting virtueSee an Inquiry into the Influence of Phyſical Cauſes upon the Moral Faculty, by Benjamin Ruſh, M. D. profeſſor of the theory and practice of medicine in the college of Philadelphia, &c, &c. .

HE is chaſtened alſo with pain upon his bed, and the multitude of his bones with ſtrong painJob, chap. xxxiii. ver. 19. . The wiſe and the learned will not deſpiſe inſtruction, however mean and trifling the vehicle may be that conveys it; for great advantages may, perhaps, be derived even from an extravagant flight of the imagination, or of any other faculties of the mind, in a dream.

HAVING finiſhed the ſubject of dreams, and the effects of dreams on the faculties of the mind, and having alſo proven that they occur in a ſtate of morbid ſleep, it now remains, in the fourth place, to point out the cauſes of dreams. Theſe may be divided into external and internal cauſes.

FIRST. Under the head of the external cauſes, I ſhall conſider thoſe which affect the outward ſenſes, either from an exceſs or deficiency of their ſtimulant powers: And,

SECONDLY. Under the head of the internal cauſes, I ſhall mention thoſe which affect the internal ſenſes likewiſe, either from their exceſs, or deficiency, of ſtimulant properties, and convey new impreſſions to the ſenſorium commune, and beget new ideas, or excite thoſe into action, already eſtabliſhed in the mind.

FIRST. I ſhall conſider thoſe external cauſes, which, if applied in exceſs, run the excitement beyond that point at which profound ſleep commences.

THESE are ſuch as exceſſive bodily fatigue, too great heat accumulated in the room, either from the ſun, fire, or bed-clothes, exceſſive eating of rich and nouriſhing food, and too free uſe of fermented, or ſpirituous, liquors; too pure or dephlogiſticated air; worms in the alimentary paſſage; a great abundance and velocity of rich blood; an accumulation of urine in the bladder; an accumulation of the venereal ſtimulus; a retention of the perſpirable matter under the cuticle: In ſhort, a retention of any of the excretions, may prove cauſes of dreams.

SECOND. I ſhall mention thoſe external cauſes whoſe ſtimulant effects ſtop ſhort of that point, at which ſleep of the ſalutary kind begins.

THESE are ſuch as idleneſs, cold, any way introduced, darkneſs, ſilence, too long abſtinence either from eating or drinking, or, rather, a deficiency of the ſtimulant effects of theſe powers; an uneaſy poſition of the body in time of ſleep; tumors ſituated externally on, or in the neighbourhood of, the trachea; ligatures on any part of the body; air rendered very impure, from its being impregnated with any noxious particles; obſtructed nares, either from mucous, or polypi, or any other ſubſtance impacted in, and ſhutting up, their paſſage; a penury of blood, and an exceſſive evacuation of any kind.

I SHALL proceed, in the laſt place, to take notice of the ſecond head, under which the internal cauſes are to be mentioned.

FIRST. I ſhall mention thoſe internal cauſes, which operate from their exceſſive ſtimulus, favouring that degree of excitement which conſtitutes morbid ſleep. Theſe are, long and intenſe applications of the mind to ſtudy or buſineſs of any kind, violent paſſions of the mind, as love, joy, and anger.

SECOND. I ſhall conclude this ſubject, with pointing out thoſe internal cauſes, whoſe ſtimulus ſtops ſhort of that point, at which refreſhing ſleep commences. Theſe are, a kind of inactivity, ſluggiſhneſs, or rather a vacancy of the mind; the depreſſing paſſions, as grief, fear, and ſhame, or rather an abſtraction of confidence.

HAVING concluded this diſſertation, I cannot lay down my pen without embracing this favourable opportunity, of publicly returning my ſincere thanks to the worthy Profeſſors of the College of Philadelphia, and of acknowledging the many valuable and important truths delivered from their different chairs in this ſeminary—Hoping, that her ſons may have treaſured up in their minds the true principles of the ſcience; that they may live as riſing monuments, to the honor of medicine; and not conclude their earthly exiſtence, till after they have extended their improvements to ſuch a length, as will mark a glorious epoch in the annals of time.