SECT. XVIII. 15. 0F SLEEP. 163 



about twenty-two years of age, who feldom fleeps more than an 

 hour without experiencing a convulfion fit; which ceafes in 

 about half a minute without any fubfequent ftupor. Large 

 doles of opium only prevented the paroxyfm, fo long as they 

 prevented him from fleeping by the intoxication, which they in- 

 duced. Other medicines had no effect on him, He was gently 

 awakened every half hour for one night, but without good ef- 

 fect, as he foon flept again, and the fit returned at about the 

 fame periods of time, for the accumulated fenforial power, which 

 occasioned the increafed fenfibility to pain, was not thus exhauft- 

 ed. This cafe evinces that the fenfibility of the fyftem to in- 

 ternal excitation increafes, as our ileep is prolonged ; till the 

 pain thus occafioned produces voluntary exertion ; which, when 

 it is in its ufual degree, only awakens us j but when it is more 

 violent, it occafions convulfions. 



The cramp in the calf of the leg is another kind of convul- 

 fion, which generally commences in fleep, occafioned by the 

 continual increafe of irritability from internal ftirnuli, or of fen- 

 fibility, during that ftate of our exigence. The cramp is a vi- 

 olent exertion to relieve pain, generally either of the Ik in from 

 cold, or of the bowels, as in fome diarrhoeas, or from the muf- 

 cles having been previoufly overflretched, as in walking up or 

 down fteep hills. But in thefe convulfions of the mufcles, which 

 form the calf of the leg, the contraction is fo violent, as to occa- 

 fion another pain in confequence of their own too violent con- 

 traction, as foon as the original pain, which caufed the contrac- 

 tion, is removed. And hence the cramp, or fpafm, of thefe 

 mufcles is continued without mtermiflion by this new pain, un- 

 like the alternate convulfions and remiflions in epileptic fits. 

 The reafon, that the contraction of thefe mufcles of the calf of 

 the leg is more violent during their convulfion than that of oth- 

 ers, depends on the weaknefs of their antagonift mufcles ; for 

 after thefe have been contracted in their ufual ad ion-, as at every 

 ftep in walking, they are again extended, not, as moft other 

 mufcles are, by their antagonifts, but by the weight of the whole 

 body on the balls of the toes ; and that weight applied ro great 

 mechanical advantage on the heel, that is, on the other end of 

 the bone of the foot, which thus acts as a lever. 



Another difeafe, the periods of which generally commence 

 during our fleep, is the afthma. Whatever may be the remote 

 caufe of paroxyfms of afthma, the immediate caufe of the con- 

 vulfive refpiration, whether in the common afthma, or in what 

 is termed the convulfive afthma, which are perhaps only differ- 

 ent degrees of the fame difeafe, muft be owing to violent volun- 

 tary exertions to relieve pain, as in other convulfions ; and the 



increafe 



