

SCT. XXIX. ii. RETROGRADE ABSORBENTS, 397 



. 



and thence do their offices very imperfectly. Thus, 

 if any one looks earneftly for fome minutes on an 

 area, an inch diameter^ of red iilk, placed on a 

 fheet of white paper, the image of the lilk will gra- 

 dually become pale, and at length totally vanifh. 



5. Nor is it the nerves of fenfe alone,as the optic 

 and auditory nerves, that thus become torpid, when 

 the ftimulus is withdrawn or their irritability de- 

 creafed ; but the motive mufcles, When they are de- 

 prived of their natural ftimuli, or of their irritabi- 

 lity, become torpid and paralytic ; as is feen in the 

 tremulous hand of the drunkard in a mo'rning j and 

 in the awkward ftep of afge; 



The hollow mufcles alfo, of which the various 

 veflels of the body are conftrudled, when they are 

 deprived of their natural ftimuli, or of their due de- 

 gree of irritability, not only become tremulous, as 

 the arterial pulfations of dying people j but alfo 

 frequently invert their motions, as in vomiting, in 

 hyfteric fuffocations, ami diabetes above defcribed. 



I muft beg your patient atteritiofk, for a few mo- 

 ments, whilft I endeavour to explain how the retro- 

 grade actions cf our hollow mufcles are the 

 confequence of their debility ; as the tremulous 

 actions of the folid mufcles are the confe- 

 quence of their debility. When, through fatigue, 

 a mufcle can act no longer, the antagonilt mufcles, 

 either by their inanimate elafticity, or by their ani- 

 mal action, draw the limb into a contrary direction : 

 in the folid mufcles, as thofe of locomotion, their 

 aftions are aflbciated in tribes, which have been ac- 

 cuftomed to fynchronous action only ; hence when 

 they are fatigued, only a fmgle contrary effort takes 

 place ; which is either tremulous, when the fatigued 

 mufcles are again immediately brought into action ; 

 or it is a pandiculation, or ft retching, .where they 

 are not immediately again brought into adiion. 



Now the motions of the hollow mufcles, as they 

 in general propel a fluid along their cavities, are af- 



P 2 fociated 



