598 



CHAP. XXVII. 



SLEEP. 



" THE faculties both of feeling and motion, possessed by the" 

 brain, " are so fatigued by their exertions in the day, that rest is 

 necessary during the night to recruit them by means of sleep & 

 the image of death," as it has been termed ; for in it we cease to 

 be cognisant of the world around and of our own existence, and 

 lie motionless. Mechanical contact, temperature, savours, odours, 

 light, and sound are no longer felt unless strong ; nor the in- 

 ternal feelings of hunger, thirst, &c. ; thought ceases, and, from 

 the general suspension of volition, gravity, no longer opposed by 

 contracted muscles, produces its full effect, the head falls for- 

 wards or to one side, the upper eyelid, the lower jaw, the ex- 

 tremities drop, and the body sinks, as far as circumstances allow 

 it, into the horizontal posture. This state may come on in a mo- 

 ment, or in a more or less gradual manner, and it may come on 

 gradually for a time and at length suddenly. If gradually, we 

 feel tired ; find attention and muscular volition more and more diffi- 

 cult, so that we imperfectly understand what we are hearing, read- 

 ing, or thinking of, or what is passing around us : we speak slowly, 

 imperfectly, and unconnectedly, till we cease to speak at all ; 

 we desire to think, perceive, and make the least exertion, no 

 longer, are drowsy. If at the same time we have a reason for 

 keeping awake, we make great and repeated efforts to open our 

 eyes, to elevate the lower jaw, and to raise and balance our head 

 and trunk, perhaps to the great amusement of others : we take 



a " Consult, besides authors hereafter to be recommended, Dr. Darwin, Zoo- 

 nomia, t. i. Sect, xviii. 



And Wienholt, Heilkraft des thierischen Magnetismus, vol. ii. p. 437. sqq. 



Fr. Aug. Ammon, Commentatio proemio regio omata de somni vigiliarumque 

 statu morboso. Gott. 182O. 4to. 



C. Fr. Heusinger, De variis somni vigUiarumque conditionibus morbosis. Isenac. 

 1820. 8vo." 



But particularly Dr. Robert Macnish, The Philosophy of Sleep. Ed. 2. Glas- 

 gow, 1834. 



