THE RELATIONS OF INSOMNIA TO 

 TYPES OF SLEEP 



By DAVID FRASER HARRIS, M.D., B.Sc. (Lond.) 

 Lecturer in Physiology, University of Birmingham 



It is admitted by all writers on sleep that more than one factor 

 is operative in producing the condition, but I do not think that 

 sufficient emphasis has been laid on the relationships between 

 the sleep-producing factors and the various types of sleepless- 

 ness. We ought to have as many types of sleeplessness as 

 we have types of sleep. 



It seems to me that just as there are several causal factors 

 productive of sleep, so there is a type of insomnia referable 

 to each of these factors. Undoubtedly normal sleep does not 

 ensue as the result of the operation of only one physiological 

 state, but rather as the consequence of the simultaneous presence 

 of several conditions, at least four of which are as follow : 



1. Relative diminution of the vigour of , the cerebral circu- 

 lation. 



2. Relative diminution or absence of sensory stimulation. 



3. Relative diminution of psychic activity. 



4. Relative increase or concentration of certain so-called 

 " fatigue-toxins." 



Now it is quite correct to say that each of these factors is 

 responsible for a particular type of sleep and is thus related to 

 a particular type of insomnia. Thus as regards the first factor, 

 enfeeblement of the cerebral circulation is the cause, for instance, 

 of the sleepiness which precedes sea-sickness, a condition 

 distinctly related to cerebral anaemia. 



Mosso,^ and Durham - long before him, demonstrated experi- 

 mentally that the cerebral cortex in sleep is in a state of relative 

 bloodlessness. There is some difference of opinion as to where 

 the short-circuited blood is accommodated. Hill ^ maintaining 



^ "Sulla circulazione del sangue nel cervello, dell' uomo,'' Rome, 1880. 

 ' " Physiology of Sleep," Guy's Hospital Reports^ i860, vol. vi. 

 ' " Mechanism of the Circulation," Text-Book of Physiology (Schafer). Pent- 

 land, 1900. 



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