682 



SLEEP. 



moderate degree of warmth favours sleep ; 

 perhaps by increasing the energy of the 

 heart's contractions, at the same time that 

 the walls of the vessels are more relaxed 

 than usual, and thus yield to the impulse. 

 A moderate degree of cold usually has the 

 opposite effect, more especially when the 

 cold is .sufficient to produce uneasy sensa- 

 tions. But cold of great severity produces 

 drowsiness, sopor, and even complete coma ; 

 apparently by producing a contracted state of 

 the superficial vessels of the body, and thus 

 occasioning an increase of sanguineous pres- 

 sure on the encephalic centres. Again, the 

 circulation of blood charged with narcotic 

 substances through the brain, is one of the 

 most powerful of all hypnotising agencies ; 

 and this, again, may produce every gradation 

 of effect, between simple sleep, from which 

 the patient may be easily aroused, and the 

 profoundest coma. One of the most com- 

 mon instances of the operation of this cause, 

 is the production of drowsiness by a deficiency 

 of ventilation ; the carbonic acid which accu- 

 mulates in the blood, when not freely carried 

 off in the air, having the properties of a pow- 

 erful narcotic. 



Phenomena of ordinary Sleep. The state 

 of perfect sleep is characterised by negative 

 rather than by positive phenomena. As al- 

 ready stated, it essentially consists in the 

 complete suspension of the sensorial powers, 

 and of all those movements in which the 

 nervous system participates, except the simply 

 reflex : with this is conjoined a partial or 

 complete suspension of the functional activity 

 of the cerebrum. According to the more or 

 less potent operation of the soporific causes, 

 will be the degree of insensibility to impres- 

 sions upon the afferent nerves. No ordinary 

 cause, as we have already shown, is so power- 

 ful as previous fatigue. Of the profoundness 

 of the sleep which may result from it, in 

 combination, perhaps, with two other agents, 

 warmth, and an atmosphere somewhat charged 

 with carbonic acid, the following remark- 

 able example may be cited from the "Journal 

 of a Naturalist." It may be proper to men- 

 tion that, the correctness of the statement 

 having been called in question, it was fully 

 confirmed by Mr. Richard Smith, the late 

 senior surgeon of the Bristol Infirmary, un- 

 der whose care the sufferer had been. " A 

 travelling man, one winter's evening, laid him- 

 self down upon the platform of a lime-kiln, 

 placing his feet, probably numbed with cold, 

 upon the heap of stones, newly put on to 

 burn through the night. Sleep overcame him 

 in this situation ; the fire gradually rising and 

 increasing, until it ignited the stones upon 



by " a state of contraction of certain muscles of the 

 neck." (See his Observations in Medicine, second 

 series, p. 27.) He does not, however, offer the least 

 proof of this hypothesis, nor does he even name the 

 muscles or veins to which he refers. We presume 

 that the platysma myoides and the external jugular 

 are meant. If so, why should not a slight com- 

 pression of the vein by any other means have the 

 e,ft"ect of producing sleep at will ? 



which his feet were placed. Lulled by the 

 warmth, the man slept on ; the fire increased 

 until it burned one foot (which probably was 

 extended over a vent-hole) and part of the 

 leg above the ancle entirely off, consuming 

 that part so effectually, that a cinder-like 

 fragment was alone remaining, and still the 

 wretch slept on ! and in this state was found 

 by the kiln-man in the morning. Insensible 

 to any pain, and ignorant of his misfortune, 

 he attempted to rise and pursue his journey, 

 but missing his shoe requested to have it 

 found ; and when he was raised, putting his 

 burnt limb to the ground to support his body, 

 the extremity of his tibia crumbled into frag- 

 ments, having been calcined into lime. Still 

 he expressed no sense of pain, and probably 

 experienced none, from the gradual operation 

 of the fire, and his own torpidity during the 

 hours his foot was consuming. This poor 

 drover survived his misfortunes in the hos- 

 pital about a fortnight ; but the fire having 

 extended to other parts of his body, recovery 

 was hopeless." It may be added that cases 

 are recorded by medico-legal writers, in which 

 defloration of a virgin, followed by concep- 

 tion, has been effected whilst she was in a 

 state of ordinary sleep, rendered unusually 

 profound by previous fatigue ; but such state- 

 ments are obviously liable to considerable 

 doubt, and scarcely appear entitled to cre- 

 dence. 



Besides the suspension of the sensorial 

 functions, however, there is usually a slight 

 diminution in the activity of the functions of 

 organic life. The heart's contractions are less 

 frequent, but the pulse is fuller. So likewise 

 the respiratory movements are diminished in 

 number; but the inspirations are deeper. 

 Less carbonic acid is produced than during 

 a similar bodily inactivity in the waking state. 

 As might be expected from these differences, 

 the amount of heat generated in the body is 

 diminished, and there is much less power of 

 resisting the effects of cold. So remarkable 

 is this abatement, that when the body is 

 exposed to intense cold (as in the well-known 

 attempt of Sir Joseph Banks and Dr. Solancler 

 to explore Terra del Fuego), " to sleep is to 

 die." There would seem, too, to be a dimi- 

 nution in the power of resisting other mor- 

 bific agencies. Thus all authorities agree that 

 sleeping in a malarious atmosphere is much 

 more liable to engender the diseases produced 

 by it, than spending the same length of time 

 in the same place, but in the waking state. 

 As a general rule, it would seem that the 

 secreting processes go on with diminished 

 activity during sleep ; but to this the cuta- 

 neous transpiration is an exception, so that, 

 in debilitated states of the system, a profuse 

 sweating often occurs as soon as the patient 

 falls asleep. From this diminished activity 

 of the organic functions it happens that hun- 

 ger is not renewed so speedily after sleep as 

 when the same number of hours have been 

 passed in watching ; a fact well known to 

 those who are liable to suffer habitually or 

 occasionally from the want of food. In this 





