CLASS!. 3. i. OF IRRITATION. 131 



ORDO III. 



Retrograde Irritative Motions. 



GENUS I. 

 Of the Aliment dry CanaL 



THE retrograde motions of our fyftern originate either from 

 .defect of ftiinulus, or from defeat of irritability. Thus ficknefs 

 is often induced by hunger, which is a want of ftimulus ; and 

 from ipecacuanha, in which lad cafe it would feem, that the 

 ficknefs was induced after the violence of die ftimulus was aba- 

 ted, and the confequent torpor had fucceeded. Hence, fpice, 

 opium, or food, relieves ficknefs. 



The globus hyftericus, falivation, diabetes, and other inver- 

 fions of motion attending hyfteric paroxyfms, feem to depend 

 on the want of irritability of thofe parts of the body, became 

 they are attended with cold extremities, and general debility, and 

 are relieved by wine, opium, fteel, and fleih diet ; that is, by 

 any additional ftimulus. 



When the longitudinal mufcles are fatigued by long action, or 

 are habitually weaker than natural, the antagonift mufcles re- 

 place the limb by ftretching it in a contrary direction ; and as 

 thefe mufcles have had their actions aflbciated in fynchronous 

 tribes, their actions ceafe together. But as the hollow mufcies 

 propel the fluids, which they contain, by motions aflbciated in 

 trains ; when one ring is fatigued from its too great debility, and 

 brought into retrograde action ; the next ring, and the next, 

 from its aflbciation in train falls into retrograde action. Which 

 continue fo long as they are excited to act, like the tremors of 

 the hands of infirm people, fo long as they endeavour to act. 

 Now as thefe hollow mufcles are perpetually (timulated, thefe 

 retrograde actions do not ceafe as the tremors of the longitudi- 

 nal mufcles, which are generally excited only by volition. 

 Whence the retrograde motions of hollow mufcles depend on 

 two circumflances, in which they differ from the longitudinal 

 mufcles, namely, their motions being aflbciated in trains, and 

 their being fubject to perpetual ftimulus. For further eluci- 

 dation of the caufe of this curious fource of difeafes, fee Sect. 

 XXIX. ii. 5. 



The fluids difgorged by the retrograde motions of the various 

 vafcular mufcles maybe diftinguilhed, i. From thofe, which 

 are produced by fecretion, by their not being attended by increafe 



