DISCOVERY 



241 



sensations is strikingly shown in a case known as 

 " Striimpell's boy." This boy, aged sixteen, hving 

 in Leipzig, suffered from the following defects : He 

 was insensitive to touch, he had no sense of smell or 

 taste, he had no muscular sense, no sense of pain, 

 and, finally, he was deaf in the right ear and blind in 

 the left eye. When his left ear was stopped up and his 

 right eye bandaged, he fell asleep in two or three 

 minutes. This negative sensory sleep factor is virtu- 

 ally the not engaging of consciousness with sensory 

 activit}-. 



Now the existence of long-continued, not too 

 intense sensory stimulation comes to the same thing 

 practically- as not engaging the attention at all. Thus 

 droning reading or preaching ceases in time to engage 

 the attention, and we fall asleep. Any long-continued 

 sensation which does not change in intensity — contact 

 of our clothes, the presence of still air at the tempera- 

 ture of the body — ceases to be a stimulus at all. Thus 

 we can sleep in the rattle of a train or the creaking of 

 a steamer, but as soon as either stops we wake up. 

 The change from noise to no noise is the stimulus. 

 Hence a person accustomed to sleep in the din of a 

 city, often cannot get off to sleep the first night in the 

 country — the stillness of the country being by contrast 

 the stimulus itself. 



Before we leave the second factor we might note that 

 in the unconsciousness of deep sleep pain itself is 

 abolished for the time being in the sense that an uncon- 

 scious bram cannot perceive pain. Our chief trouble 

 is to induce sleep in cases of great pain (neuralgias, 

 tic douloureux, sciatica, etc.), but, having induced it, 

 we know that the patient will obtain complete relief. 

 Hence Shakespeare is quite right when he says : " He 

 that sleeps feels not the toothache " {Cymbeline, 

 Act V, sc. 4). Of course this is equally true of mental 

 pain : 



"Come sleep . . . the balm of woe, 

 . . . the prisoner's release" — 



says Sir Philip Sidney in Astrophel and Stella. In 

 the same strain, Shakespeare declares — 



" ' Sleep no niore ! . . . 

 Macbeth does murder sleep,' the innocent sleep. 

 Sleep that knits np the ravell'd sleave of care, 

 The death of each day's life, sore labour's bath. 

 Balm of hurt minds, great nature's second course. 

 Chief nourisher in life's feast." 



{Macbeth, Act II, sc. 2). 



(3) Absence of Thought 



Very closely allied to the absence of sensations as 

 a cause of sleep is the third factor, the absence of 

 thoughts, emotions, ideas, any cerebral activities, in 

 fact. Everybody knows that anything that is on the 

 mind will prevent sleep, whether it be joy, grief, or an 



unsolved mathematical problem. Thoughts we cannot 

 banish keep us awake ; the tranquillity of a mind 

 at rest, at ease, " at leisure from itself" conduces to 

 sleep. It is the insomnia related to this third factor 

 that is so familiar in the sleeplessness of a " bad con- 

 science," as it is jocularly called. It is mental activity, 

 of course, which keeps children awake after their 

 first visit to the menagerie, pantomime, or '' hall of 

 mysteries." The personal factor here is interesting; 

 some people pass a sleepless night if they know they 

 have to get up earlier than usual next morning ; some 

 condemned criminals have slept soundly the night 

 before their execution. As long as the mind is 

 obsessed, sleep is impossible. Sleep means inactivity 

 of the brain, thoughts involve its activity, therefore 

 thoughts and sleep are mutually exclusive. 



"Care keeps his watch in every old man's eye. 

 And where care lodges, sleep will never lie." 



(Romeo a:id Juliet, Act II, sc. 3.) 



Wordsworth described this insomnia of the thu'd 

 factor well when he addressed sleep as " Still last to 

 come where thou art wanted most." 



(4) Less Energetic Circulation 



We ma^' now inquire into the fourth and last cause 

 of sleep, which is the diminution in energy of the circu- 

 lation of the blood in the brain. Functional activity 

 of a part depends on a certain amount of blood sup- 

 plied to the part ; in health the more blood an organ 

 gets the more active it is. The brain is no exception ; 

 as its blood supply falls off, its activity is diminished 

 until at last sleep supervenes. 



Some of the evidence that the blood-supply of the 

 brain is reduced in sleep is direct. It has been noticed 

 through a wound of its skuU that the brain (cortex 

 cerebri) of a dog becomes paler during sleep. Physiolo- 

 gists have trephined the dog's skull and inserted a 

 glass window into the aperture. They have noticed 

 that when the dog fell asleep the surface of the brain 

 not only became paler but receded from the glass, 

 which previously it had pressed upon. Every 

 mother knows that in the infant's head there is a 

 membranous spot (the anterior fontanelle) which moves 

 up and down with the same rhythm as the child's 

 breathing. 



Obviously the more blood in the child's brain, the 

 more will this membrane bulge up ; now it can be seen 

 that this membrane is depressed during sleep and 

 raised during wakefulness. When the child cries, 

 and so prevents the veins from the head emptying 

 their blood easily into the heart, the blood so dammed 

 back causes the fontanelle to bulge upwards. 



The Russian physiologist, Tarchanoff, has proved 



