Covjeclures on the proximate Cause of Sleep. £57 



constitute that which is called dreams, which are more or less 

 complicated according to the number of the active organs*." 



This, on a comparison with the preceding opinions, appears 

 to be a probable and satisfactory explanation, as far as it goes ; 

 but our curiosity requires a more detailed elucidation of the na- 

 ture of sleep. It may properly be said, that it is rest after fa- 

 tigue; but we know that it is something more. We can rest when 

 it is necessary, without that intense and predominant change 

 which locks up our senses and intellect, and envelops us with in- 

 advertence and oblivion of the past, present, and future. We 

 cannot reflect on the nature of this state, without being satisfied 

 that it involves some important vital process, so indispensable as 

 to be of daily recurrence, and of such general influence as to en- 

 gage every part of the frame, but particularly the organs of think- 

 ing, sensation, and voluntary motion. If we ask ourselves what 

 process is of prime necessity to those organs, we can answer with- 

 out difficulty, tkat which repairs their waste, and preserves their 

 consistence and vigour — the process of assimilation. Whatever 

 may be the result of its operation in the bones and muscles and 

 other coarser parts of the body, we can scarcely reflect on its ac- 

 tion upon the delicate texture of the brain and nerves, without 

 perceiving that it must be accompanied bv powerful and over- 

 whelming effects. These are the fragile instruments of thought, 

 feeling, and motion ; and no wonder that a change which affects 

 their very structure should be attended with a cessation of their 

 functions, and the qcImA paralysis of sleep. 



Yet this is but a conjecture; and so obscure and inaccessible is 

 the subject, that, however we may wish for certainty, we must be 

 contented with mere plausibility. There is no decisive fact to 

 support the position ; and, like first principles, if its own reason- 

 ableness does not carry with it conviction, it must, for the pre- 

 sent, remain destitute of proof. Still we ought not to disregard 

 any phienomenon that may lead to clearer views of the subject. 

 Most animals sleep shortly after their meals; and there are few 

 climates in which men do not allow themselves the same indul- 

 gence. In these countries, this is not so generally the practice; 

 and it may be a question, whether it is not by an effort that we 

 at first acquire a habit not natural to us, and overcome one which 

 we originally found to be almost irresistible, and to which, per- 

 haps, we should be compelled to submit, if we were not able to 

 interrupt or suspend the process of assimilation in the nervous 

 system. It is true that we can have no direct influence over this 

 process iu the grosser parts of the frame ; but our power may be 

 more extensive in the scat of the intellect. By an effort we can 



• Spurzheim's Physiognomy, 1st edition, p. 216. 

 Vol. 54. No. 258. Oct. 1819. R continue 



