Sect. XXIX. n. J; ABSORBENTS. 269 



ura! quantity of their adapted ftimuli. — Thus the eye is inca- 

 pab-e of feeing objects in nn obfeure room, though the iris is 

 quite dilated, after having been expoied to the meridian fun. 



3. There is a third law of irritation, that all the parts of our 

 todies, which have been lately iubjected to lefs ftimulus, than 

 they have been accu-ftomed to, when they are expofed to their 

 ufuii quantity of ftimulus, are excited into more energetic mo- 

 tions : thus when we come from a dufky cavern into the glare of 

 daylight, our eyes are dazzled ; and after emerging from the cold 

 bath, the fkin becomes warm and red. 



4. There is a fourth law of irritation, that all the parts of our 

 bodies, which are fubjectcd to ft ill ftronger ftimuli for a length 

 of time, become torpid, and refufe to obey even thefe llronger 

 ftimuli ; and thence do their offices very imperfectly. — Thus, if 

 any one looks earneftly for fome minutes on an area, an inch di- 

 ameter, of red filk, placed on a meet of white paper, the image 

 of the filk will gradually become pale, and at length totally vaniih. 



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

 tory nerves, that thus become torpid, when the ftimulus is with- 

 drawn or their irritability decreafed ; but the motive mufcles, 

 when they are deprived of their natural ftimuli, or of their irri- 

 tability, become torpid and paralytic ; as is feen in the tremulous 

 hand of the drunkard in a morning °, and in the awkward ftep 

 of age. 



The hollow mufcles alfo, of which the various veiTels of the 

 body are constructed, when they are deprived of their natural 

 ftimuli, or of their due degree of irritability, not only become 

 tremulous, as the arterial pulfations of dying people ; but alfo 

 frequently invert their motions, as in vomiting, in hyfteric fuffo- 

 cations, and diabetes above defefibed. 



I muft beg your patient attention, for a few moments, whilft 

 I endeavour to explain, how the retrograde actions of our hol- 

 low mufcles are the confequence of their debility; as the tremu- 

 lous actions of the folid mufcles are the confequence of their de- 

 bility. When, through fatigue, a mufcle can act no longer ; the 

 antagonift mufcles, either by their inanimate eiafticity, or by 

 their animal action, draw the limb into a contrary direction : in 

 t\ie folid mufcles, as thofe of locomotion, their actions are aflb- 

 ciated in tribes, which have been accuftomed to fynchronous ac- 

 tion only ; hence when they are fatigued, only a fingle contrary 

 effort takes place ; which is either tremulous, v/hen the fatigued 

 muiclss are again immediately brought into action ; or it is a 

 pandiculation, or ftretching, where they are not immediately 

 in brought into action. 



Now the motions of tie hollow mufcles, as they in general 



propel 



