AN
INAUGURAL DISSERTATION
ON
SLEEP AND DREAMS
THEIR
EFFECTS ON THE FACULTIES OF THE MIND
AND THE
CAUSES OF DREAMS.
SUBMITTED TO THE EXAMINATION
OF THE
REV. WILLIAM SMITH, S. T. P. PROVOST
THE
TRUSTEES AND MEDICAL PROFESSORS
OF THE
COLLEGE of PHILADELPHIA
FOR THE DEGREE OF
DOCTOR OF MEDICINE:
ON THE TWENTY-THIRD DAY OF JUNE, A. D. 1791.
BY SAMUEL FORMAN CONOVER.
OF THE STATE OF NEW-JERSEY,
MEMBER OF THE MEDICAL SOCIETY OF SAID STATE,
AND OF THE
AMERICAN MEDICAL SOCIETY OF PHILADELPHIA.
PRINTED BY T. LANG, NO 21, CHURCH-ALLEY.
MDCCXCI. 



TO
BENJAMIN RUSH, M. D.
PROFESSOR OF THE THEORY AND PRACTICE OF MEDI-
CINE IN THE COLLEGE OF PHILADELPHIA, &C. &C.
TO
CASPER WISTAR, M. D.
PROFESSOR OF CHEMISTRY AND PHYSIOLOGY IN THE
COLLEGE OF PHILADELPHIA, &C. &C.
AND TO
BENJAMIN SMITH BARTON, M. D.
PROFESSOR OF NATURAL HISTORY AND BOTANY IN THE
COLLEGE OF PHILADELPHIA, &C. &C.
Men,
Who have approved themselves friends to the science
of Medicine,
Under whose fostering hands I have been nurtured in
the legitimate principles of their respective
branches of medical knowledge,
AND
Whose humanity, liberality, and great ability to re-
lieve the distressed, and to smooth the avenues to
death, render them not only respectable in
their professions, but also useful and
worthy members of society,
THIS DISSERTATION IS,
With all due respect and gratitude,
Inscribed,
By their much indebted friend,
and devoted servant, and pupil,
The Author.



ON
SLEEP AND DREAMS.
THE subject of SLEEP, like many other subjects in
medicine, cannot be reduced to the principles of ma-
thematical 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 study *" 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, en-
" tirely 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 excitement †." That
there is a certain degree of excitement, necessarily ex-
isting 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 ex-
citement, different from the foregoing, favouring pro- 
found sleep, which is produced by certain powers ope- 
rating on the living property inherent in every animal.
This property has received different names, from diffe-
rent authors. It is called by Baron Haller the vis in-
sita ; by Dr. Cullen, the nervous power ; by Mr. John
B Hunter, 
* On the Human Understanding.
† First Lines of the Practice of Physic, vol. iv. pag. 127. 

8 ON SLEEP.
Hunter, stimulability ; and by Dr. Brown, the excitabi-
lity. The exciting powers acting on the excitability,
producing excitement favourable to health, and in-
viting sleep, if carried beyond their proper bounda-
ries, or withheld, occasion morbid sleep, disease, and
even death itself. The sleep-inviting point, or that de-
gree 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 ex-
plain. " Sleep, then, is the effect of the actions of
" the day, at first always giving more and more ex-
" citement, but less and less in proportion to the con-
" tinuance of their operation, but in such a sort as al-
" ways 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 ex-
" ists." 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 mo-
derate, 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 pro-
ducing it, is certain. By all unusual exertions, those
unaccustomed to fatigue, &c. will have their sleep hur-
ried or produced sooner than in common, and it is ge-
nerally of the morbid kind.
A MAN of science and of genius, in the pursuit of
mental acquirement, stimulated by the spirit of emu-
lation, 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 ac-
commodated 

9 ON SLEEP.
commodated to the excitability then existing in the
system, favouring the waking state *. 
I THINK it has been sufficiently proven, that the
causes producing profound sleep, or sleep without dream-
ing, 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 as- 
" sertion. 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 re- 
" semblance 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 phænomenon of sleep in chil-
dren be explained upon other physical causes, and not
upon the want of reflex-sensation ? That the excita-
bility of a child is more abundant, cannot, or will not,
I imagine, be denied; and from this I may justly in-
fer, 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
* See Dr. Brown's Elements of Medicine, in note of § xxxi.

10 ON SLEEP.
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 in-
tervals 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 health *.
THE sudden transition from sleeping to waking, and
vice versa, is more observable in some persons, under
certain circumstances, than in others ; and these sud-
den 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 reco-
" vered." From the theory of sleep which I have en-
deavoured to establish, may not these facts be resolved
upon the same physical causes partially influencing the
system, and producing an unequal excitement and mor-
bid 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 consti-
stitutes
* This 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 ad-
mitted 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 for-
mer than among the latter. 

11 ON SLEEP.
tutes the disease. How does it come about, that every
thing which stimulates produces that effect by its sti- 
mulant, and not by its sedative, virtue ? Let those ac-
customed 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 stimu- 
lating rays of light, and the noise of the busy world, 
who eats and drinks his hard earnings with a good ap- 
petite, 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 fatigue *."—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 fore-
going, 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 ex-
planation.
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 phy-
sical principles as all other stimuli, producing a partial
exhaustion of the excitability, and favouring the sleep 
inviting
* A Treatise on Experience in Physic. vol. ii. 

12 ON SLEEP.
inviting point, and not upon the effects of sound sim-
ply 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 preced-
ing 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 sti-
mulus, or hurtful power, that may be applied.
This living principle, inherent in the world of ani-
mals, 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 physiologist * the world has
hitherto produced, did not, indeed, admit of irritability
in vegetables; but the industry and sagacity of the Bo-
tanists have shewn us, that there is a very considerable
number of vegetables, which exhibit signs of irritabi-
lity, 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 pre-
sent 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 in-
voluntary 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.
* Barron Haller.

13 ON SLEEP.
stamina, embrace the pistil with a seemingly-venereal ap-
petite, and discharge their fecundating influence, from
the cells of the anthers, 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 *, 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 ap-
pearance 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 expand-
ed ; and, hence arises that particular state of vegeta-
bles, which constitutes what Linnæus and other na-
turalists have denominated Somnus Plantarum, or the
sleep of plants. During the continuance of this vegeta-
ble sleep, the appearance of the plant is so much chang-
ed, 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 re-
turn 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. †
IF
* The Dwarf Cistns, or Little Sun-Flower.
† Some of these hints on the irritability, voluntary nnd involuntary motions
of vegetables, were suggested to me by Benjamin Smith Barton, M. D. Pro-
fessor of Natural History and Botany in the college of Philadelphia, &c. &c. 

14 ON SLEEP.
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 unphiloso-
phical 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 like-
wise will further enable us, to point out the impropri-
ety of the conjugal pair gratifying or indulging the
hymeneal pleasures in the morning. Thus, the tem-
perature 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 sti-
" mulus 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 valu-
able facts, concerning the Hybernation of animals, which
will, beyond all scruple, help to resolve many phœno-
mena in nature, shew the great sedative power of cold,
and the effects it has in producing sleep, in many fami-
lies of the animal kingdom. By the term Hybernation,
is to be understood, that dormant state in which ani-
mals of many different kinds, subsist in winter without
food, 

15 ON SLEEP.
food, without any apparent motion, and without sense,
seemingly sound asleep, and not recoverable from it 
unle s placed in a warmer atmosphere. It is to be ob-
served, 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 ani-
mals, 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 like- 
wise several quadrupeds, which are remarkable for re- 
maining during winter in a torpid state, such as the
bear, the badger, the squirrel, the hedge-hog, the dor- 
mouse, 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 ex- 
periments, it does not appear that the blood of the 
bear, of the hedge-hog, of the badger, or of the dor- 
mouse, 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 secre-
tions, are very much diminished. This is the most plau-
sible 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 ani-
mal is reduced from 103 to 80 of the scale of Fahren-
heit.*—In the hamster, Sulzer has shewn us, that
during the summer season, the pulse beats one hundred
and
* See Nova Commentaria Academiæ Petropolitanæ, tom. xiv.

16 ON DREAMS.
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 minute *.
This last observation does not apply merely to the ham-
ster, 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 in-
ferior animals : the influence of a cold climate on the
human pulse is prodigious. It has been found, for ins-
tance, that the heart of the Greenlander does not beat
more than thirty, or forty, strokes in a minute†.
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 ac-
tually 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 ob-
servations, I finish the subject of sleep, and now pro-
ceed, 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 de-
pends upon causes producing a certain degree of ex-
citement favourable to the point at which sleep com-
mences, 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 par-
tially suspended. Dreams may be explained, likewise,
upon the same method of reasoning, as sleep. Certain
powers
* Naturgesch. des Hamsters, pag. 169.
† Blumenbachii Institutiones Phys 

17 ON DREAMS.
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 philoso-
phers, 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 func-
tions in the waking state, and that, in time of morbid 
sleep, there is either a deficiency or an excess of ex-
citement, with respect to the different functions, in
different degrees. In such an intermediate state of de- 
ficiency or excess of excitement in the brain, then
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 be- 
yond 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 di-
ferent degrees of excitement: the one is owing to 
excessive, and the other to a deficient, degree of excite- 
ment 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 

18 ON DREAMS.
and trifling causes. A labouring man seldom dreams
much. " The sleep of a labouring man is sweet, whe-
" ther he eats little or much, but the abundance of the
" rich will not suffer him to sleep *". 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 me-
" mory, who told him, he had never dreamed in his
" life, till he had that fever he was then newly reco-
" vered of, which was about the five or six and twen-
" tieth year of his age." And, as a farther corroborat-
ing 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 together †". 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 un-
questionably 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 excita-
ble to new impressions from causes suggested from
without, and certainly they may beget new ideas with-
in, and likewise excite those into action already fixed
on the mind, though, for the most part, incoherent.
IT
* Ecclesiastes, chap. v. ver. 12.
† Locke on the Human Understanding, vol. i. pag. 76. sect. 17. 

19 ON DREAMS.
It has been observed, in the former part of this dis-
sertation, 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 af-
fected by any stimuli, that may be at that time applied.
This will, perhaps, enable us to explain more satisfac-
torily the phenomenon of dreaming, at the approach
of day, than at any period of the night; for it is ge-
nerally 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 Disserta-
tions Moral and Critical. He observes, that " particular 
" dreams might be accounted for from impressions
" made in time of sleep on the organs of sense, parti- 
" cularly those of touch and feeling. A very slight 
" hint, suggested from without, or in any way suggest-
" ed, is sufficient for fancy to work upon, in produc-
" ing 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 quar-
" rel to the firing of a pistol, which they put in his
" hand for that 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 gentle-
man 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 

20 ON DREAMS.
" and assume the appearance of a rising full moon.
" Upon the appearance of this singular phenomenon,
" I thought my dog started in pursuit of it. Immedi-
" ately 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 garb : 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 fur-
" ther, 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 judi-
cious induction of the effects of these facts, are suffi-
cient to prove the astonishing vivacity of the imagina-
tion, 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 excite-
ment, 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 oc-
cupying 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 parti-
ally 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 intel-
lectual 

21 ON DREAMS.
lectual 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 facul-
ties, some are more, others less, affected, and some ap-
pear 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 understand-
ing 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 perplexi-
ties, 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 facul-
ties, 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 en-
tirely lost our moral faculty. Hence, we sometimes
dream of perpetrating crimes without scruple or re-
morse ; crimes, both repugnant to law and to gospel,
and at which we should shudder when awake. Would
it 

22 ON DREAMS.
it be admitted, if I were to ascribe this to the deser-
tion 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 o-
verturn, and retard the progress of, the Christian reli-
gion, 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 be-
lieve, " 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 ? " Su-
" perstition is one of the worst diseases of the soul. It
" is generally unfriendly to happiness, to rational pie-
" ty, and to sound philosophy *". 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 institut-
ted physical evil for the eradication of moral evil.
May not, then, bodily and mental pain, which are fre-
quently experienced in dreams, be of use to those per-
sons 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 extir-
" pating vice and promoting virtue †".
" HE
* See Dr. Beattie's Dissertations Moral and Critical.
† See 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 Philad 

23 ON DREAMS. 
" He is chastened also with pain upon his bed, and
" the multitude of his bones with strong pain *". The
wise and the learned will not despise instruction, how- 
ever 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 ef- 
fects of dreams on the faculties of the mind, and hav-
ing 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, ei- 
ther 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 sti-
mulant 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, li-
quors ; too pure or dephlogisticated air; worms in the 
alimentary passage; a " great abundance and velocity 
" of rich blood ;" an accumulation of urine in the
D bladder
* Job, chap.xxxiii. ver. 19. 

24 ON DREAMS.
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 eat-
ing or drinking, or, rather, a deficiency of the stimu-
lant 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 ; ob-
structed nares, either from mucous, or polypi, or any
other substance impacted in, and shutting up, their pas-
sage ; 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
but 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 vacan-
cy of the mind ; the depressing passions, as grief, fear,
and shame, or rather an abstraction of confidence. 

25 CONCLUSION.
HAVING concluded this dissertation, I cannot lay
down my pen without embracing this favourable oppor-
tunity, 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 semi-
nary—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 medi-
cine ; and not conclude their earthly existence, till af-
ter they have extended their improvements to such a
length, as will mark a glorious epoch in the annals of
time.