Conjectures on the proximate Cause of Sleep . 331 



the day, return to them again in resistance and interruption of 

 the process in question? Is it even impossible that the subject 

 of reflection may have occupied it, without an interval, from the 

 moment of retiring to rest, even though all the other organs may 

 have sunk into repose ? May not this incessant activity continue, 

 for several davs, to the detriment of the health ? may it not even 

 involve the entire l)rain, and, by preventing the accession of sleep, 

 terminate at last in mental derangement ? 



Thus, however weighty and formidable these objections ap- 

 peared, instead of subverting, they all contribute their aid to sup- 

 port the hypothesis. 



But is it in the contemplation of those who dissent from these 

 opinions to maintain that sleep is nothing more than repose after 

 fatigue — that there is no other difference between waking and 

 sleeping, than between labouring and abstaining from labour; and 

 that there is no important vital process operating on the instru- 

 ments of sensation, voluntary motion, and intelligence ? If they 

 allow that there is some such process, I should be glad they would 

 point it out ; and if it better accounts for these various phaeno- 

 mena than that of assimilation, I shall willingly relinquish my 

 hypothesis in favour of theirs. 



Will it be contended that the whole brain and nervous system 

 may sleep during dreams? Then why are not dreams the con- 

 stant attendants on sleep ? Why are not all our visions accom- 

 panied by night-mare ? and why is sonmambulism so rare an oc- 

 currence ? Will it, on the other hand, be averred that the whole 

 of the brain mav be awake while the residue of the man is asleep ? 

 Let this be admitted — hut, if so, why are not the nerves of the 

 senses and voluntary motion, which bear so strong an analogy to 

 the brain, in substance and office, equally wakeful ? Why are we 

 not always in communication with the external world; or, in other 

 words, Why are we not always awake ? The process of assimila- 

 tion relieves us from these difficulties, and shall we still lie inclined 

 to reject it ? Perhaps, on these considerations, my hypothesis 

 may happen to find favour, and that of Gall and Spurzheim be 

 discountenanced: — perhaps it will be asserted that the assimilat- 

 ing process may lock up in sleep those parts of the brain allotted 

 to reflection, judgement, and will, but leave to the active enjoy- 

 ment of its inmates the local habitation of the imagination and 

 fancy. Even this would lie a more plausil)le conjecture, than the 

 incongruous theory which insists that at the same moment the 

 «ouI can be partially awake and asleep ; but there is as little foun- 

 dation, in iiutiiic, for the one as the other. Gall sought with in- 

 defatigable perseverance and adequate sagacity, for some external 

 indication of the seats of those faculties, but none could i)e found; 

 yet hi» labour did not go unrewarded. It led him to more for- 

 tunate 



