SLEEP 149 



is probably to be found in the diminished oxygen intake 

 and therefore diminished generation of neuro-electricity, 

 rather than in vaso-motor fatigue. 



Halliburton says : " Sleep has been attributed by some 

 to changes in the blood supply of the brain, and ultimately 

 referred to fatigue of the vaso-motor centres. The exis- 

 tence of an effective vaso-motor mechanism in the cerebral 

 blood-vessels themselves is problematical ; so that if changes 

 occur in the cerebral blood pressure or rate of flow, they 

 are mainly secondary to those which are produced in other 

 parts of the body. Plethysmographic records from the 

 arm of a sleeping man show a diminution of its volume every 

 time he is disturbed, even though the disturbance may not 

 be sufficient to awaken him. This is interpreted as meaning 

 a diminution in the blood of the body, and a corresponding 

 increase in the blood flow through the brain. It is, however, 

 quite possible that the vascular condition is rather the 

 concomitant or consequence of sleep than its cause." 



We may be quite clear upon one point ; whether the 

 vascular condition is or is not a consequence of sleep, the 

 blood is the carrier of energy and increased blood-flow 

 must mean increased brain potential. 



" Some of the theories," continues Halliburton, " to 

 account for sleep have been chemical. Thus certain 

 observers have considered that sleep is the result of the 

 action of chemical materials produced during waking hours, 

 which have a soporific effect upon the brain ; according to 

 this theory awakening from sleep, is due to the action of 

 certain other materials produced during rest, which have 

 the opposite effect." 



According to this theory also one would need, for these 

 chemical processes to continue an undeviating course 

 throughout life, to eat and drink exactly the same things 

 day by day ! 



" Obersteince has gone so far as to consider that the 

 soporific substances are acid in nature, and others regard 

 them as alkaloidal." 



It is difficult to follow the reasoning here and I quite 

 agree that theories such as these rest upon the flimsiest 



