274 ^ 0^ SLEEP, DREAMING, 



applied at the one end or at the other, the end terminating externally on 

 that connected with the brain : and hence, internal excitements, as those 

 of severe study, intense grief, undue eating or drinking, or febrile diseases, 

 produce the same effect as causes operating from without. 



In either case, tlie sleep or torpitude produced is sound or healthy 

 imder a certain degree of exhaustion alone : hence, mankind sleep most 

 refreshingly after moderate or accustomed fatigue, moderate or accus- 

 tomed study, moderate or accustomed meals. 



If the stimulus be a little increased beyond this medium, an undue and 

 morbid proportion of sensorial power is secreted, which postpones, indeed, 

 the torpitude or sleep for the present, but at the expense of the general 

 strength of the system, and an expense to which, the vital organs them- 

 selves contribute something: whence a far deeper and heavier sleep or 

 torpitude ensues than would have ensued with less proportion of fatigue. 

 If such torpitude take place before the vital organs are totally exhausted, it 

 ?3 confined to the organs of sense alone, which hereby progressively recover 

 their accustomed activity and vigour .But if the vital organs be also ex- 

 hausted before the torpitude ensues, it will be propagated to themselves, 

 the living principle will cease, and the sleep will be the sleep of death. 

 Violent and continued pain or labour, as external stimuli, violent and- 

 continued fevers, violent and continued grief, a very inordinate debauch, 

 .19 internal stimuli, are all hable to produce these effects : and the one or 

 the other will take place in proportion to their excess and extremity. 



If a stimulus affecting the organs of sense, at which end soever applied, 

 be intolerably pungent or forcible, the sensorial power will be exhausted 

 immediately, and the organ directly affected will become instantly torpid. 

 Hence sounds, intolerably loud, make us deaf; excessive light blinds us ; 

 acrimonious smells or savours render us incapable of smelling or tasting. 

 And hence an abrupt shock of joy or grief, a sudden and intense paroxysm 

 of fever, large quantities of wine or spirits, as internal causes, produce 

 morbid lethargy, palsy, apoplexy, which are only so many modifications 

 of the sleep, or torpitude of the sensitive and irritative fibres. If the same 

 abrupt and violent cause be sufficient to act upon the vital organs, as well 

 as upon those of external sensation, the torpor becomes universal, and the 

 sleep is once more the sleep of death. It is in this manner that death is 

 produced by a stroke of lightning. 



As violent stimuli produce sudden and occasionally irrecoverable tor- 

 pitude, either general or local, stimuli less violent induce a tendency to 

 the same effect. Hence the nostrils of persons not accustomed to snuff 

 are more forcibly agitated by its application, than those that have been ia 

 the use of it : the eyes of persons accustomed to sleep in the glare of the 

 sun, find no inconvenience from exposure to the fight of the morning-; 

 while those who usually sleep in total darkness are awoke by its stimulus. 

 And so of the rest. 



On this account a very small portion of light, of sound, or of exercise, 

 are sufficient sources of exhaustion to those who are not in the habit of 

 using great external or internal activity. Hence savages, and quadrupeds, 

 who use but very little internal activity, and^no more external activity than 

 is necessary to gratify their passions and satisfy their hunger, become 

 torpid upon very slight excitements. Hence infants become exhausted 

 upon still slighter excitements ; as the exercise of being carried, the mere 

 breath of the air, or the digestion of milk alone in the stomach ; either of 

 wiiich, but especially the whole coilectively, is sufficient to make th^m 



