Conjectures on the proximate Cause of Sleep. 261 



Most of the other circumstances mentioned by this writer have 

 already been adverted to, and they are all of easy and obvious ex- 

 planation upon the proposed hypothesis; for example, " indiges- 

 tion and various bodily affections produce sleeplessness *." From 

 preceding obsen'ations, it may readily be understood, that in di- 

 gestion the nutritious matter continues in the stomach, instead 

 of being carried into the system, and deposited in its due propor- 

 tion in the brain and nerves. " All mental occupations attended 

 with intense thought and great interest prevent sleep, and any 

 great affections of the mind have the same efF?ct f." The solu- 

 tion of this phaenomenon has already been given ; but it is here 

 to be noticed, that the very intensity of these meditations and 

 passions in a certain time induces sleep. They exercise and ex- 

 haust the brain, and this exhaustion renders a renewal necessary 

 by assimilation; and according to the hypothesis, this process 

 cannot act on the substance of the brain, without-occasioning 

 sleep. 



" A full repast is often followed by sleep, even in animals, as 

 dogs. The distention of the stomach excites the circulation, and 

 this brings on a condition of the brain favourable to sleep %" 

 Thiscondition, under the circumstances here noticed, can scarcely 

 be any other than the activity of the assimilating process. " After 

 the sleep has lasted long enough to restore the animal powers, 

 we awake without any change or occurrence which can be shown 

 to affect particularly the brain or other parts, of which the ac- 

 tion was suspended by sleep §." In other word^, after the ex- 

 hausted substance of the brain and nerves has been renewed by 

 the assimilating process, we awake from the sleep which was the 

 concomitant of its action. It would not be easy by any experi- 

 ment to show that any change had taken place in those parts ; 

 but the fresh vigour with which we think and act is, in some de- 

 gree, a proof of this change, and which is indeed implied in the 

 very phraseology of this writer — " the restoration of the ani- 

 mal powers." 



He adds, " There are rare examples of individuals who have 

 gone on sleeping for days, weeks, and months ; but these his- 

 tories are not accompanied with such particulars as would en- 

 able us to judge of the cause ||." It would be well worthy the 

 attention of future inquirers to ascertain whether there are such 

 facts in those cases, as would decide whether the cause of this 

 state of torpor is not the protracted duration of the assimilating 

 process: such, for instance, as the patient being overburthened 

 with the obesity of a bear or a marmot in the commencement of 

 his slumbers, and, like them, emaciated at their termination, with- 

 out any other assignable cause for the change. It is, however, a 



• Ilces'» Cyc. t Id. X Id- § I'l. II Id- 



R [i well- 



