1 68 OF SLEEP. SECT. XVIH. 20 



nious work lately publiflied by Dr. Beddoes. Who after la- 

 menting that 'opium frequently occafions reftleflhefs, thinks, 

 " that in moft cafes it would be better to induce fleep by the 

 abltraftion of ftimuli, than by exhaufling the excitability ;" and 

 adds, u upon this principle we could not have a better foporific 

 than an atmofphere with a diminifhed proportion of oxygene 

 air, and that common air might be admitted after the patient 

 was aileep." (Obferv. on Calculus, &c. by Dr Beddoes, Mur- 

 ray.) If it mould be found to be true, that the excitability of 

 the fyftem depends on the quantity of oxygene abforbed by the 

 lungs in refpiration according to the theory of Dr. Beddoes, and 

 of M. Girtanner, this idea of fleeping in an atmofphere with lefs 

 oxygene in its competition might be of great fervice in epileptic 

 cafes, and in cramp, and even in fits of the afthma, where their 

 periods commence from the increafe of irritability during fleep. 



Sleep is likewife faid to be induced by mechanic preiTure on 

 the brain in the cafes of fpina bifida Where there has been 

 a defect of one of the vertebrae of the back, a tumour is protru- 

 ded in confequence ; and, whenever this tumour has been com- 

 prefled by the hand, fleep is faid to be induced, becaufe the 

 whole of the brain both within the head and fpine becomes com- 

 prefled by the retroceffion of the fluid within the tumour. But 

 by what means a compreflion of the brain induces fleep has not 

 been explained, but probably by diminifhing the fecretion of 

 fenforial power, and then the voluntary motions become fuf- 

 pended previoufly to the irritative ones, as occurs in moil dying 

 perfons. 



Another way of procuring fleep mechanically was related to 

 me by Mr. Brindley, the famous canal engineer, who was 

 brought up to the bufinefs of a mill-wright j he told me, that he 

 had more than once feen the experiment of a man extending 

 himfelf acrofs the large ftone of a corn-mill; and that by gradu- 

 ally letting the ftone whirl, the man fell afkep, before the ftone 

 had gained its full velocity, and he fuppofed would have died 

 without pain by the continuance or increafe of the motion. In 

 this cafe the centrifugal motion of the head and feet muft accu- 

 mulate the blood in both thofe extremities of the body, and thus 

 comprefs the brain. 



Laitly, we mould mention the application of cold ; which, 

 when in a lefs degree, produces watchful nefh by the pain it oc- 

 cafions, and the tremulous convulfions of the fubcutaneous muf- 

 cles ; but when it is applied in great degree, is faid to produce 

 fieep. To explain this efFeft it has been faid, that as the veflels 

 of the fkin and extremities become firfl torpid by the want of 

 the flimulus of heat, and as thence iefs blood is circulated 



through 



