i> PRODUCTION OF IDEAS. SECT. XIV. 7, 



Add to this, that the lungs, though eafily ftimiu 

 lated into inflammation , are not fenfible to heat. 

 See Clafs, III. i. i. ic, 



VII. Of the Senfe of Extenfion. 



THE organ of touch is properly the fenfe of pref- 

 fure, but the mufcular fibres themfelves conftitute 

 the organ of fenfe, that feels extenfion. The fenfe 

 of preffure is always attended with the ideas of the 

 figure and folidity of the object, neither of which 

 accompany our perception of extenfion. The 

 whole fet of mufcles, whether they are hollow 

 ones, as the heart, arteries, and inteftines, or lon- 

 gitudinal ones attached to bones, contract them- 

 ielves, whenever they are ftimulated by forcible 

 elongation ; and it is obfervable, that the white 

 mufcles, which conftitute the arterial fyftem, feem 

 to be excited into contraction from no other kinds 

 of ftimulus, according to .the experiments of Haller, 

 And hence the violent pain in fome inflammations, 

 as in the paronychia, obtains immediate relief by 

 cutting the membrane, that was ftretched by the 

 tumour of the fubjacent parts. 



Hence the whole mufcular fyftem may be confi- 

 dered as one organ of fenfe, and the various atti- 

 tudes of the body, as ideas belonging to this organ, 

 of many of which we are hourly confcious, while 

 many others, like the irritative ideas of the other 

 fenfes, are performed without our attention. 



When the mufcles of the heart ceafe to aft, the 

 refluent blood again diftends or elongates them ; 

 and thus irritated they contract as before. The 

 fame happens to the arterial fyftem, and I fuppofe 

 to the capillaries/ inteftines, and various glands of 

 the body, 



When the quantity of urine, or of excrement, 

 <Jiften<4s the bladder, or rectum, thofe parts con- 



