Class 1. 3. 1. OF IRRITATION. r 3 a 



ORDO IU. 



Retrograde Irritative Motions* 



GENUS I. 



Of the Alimentary Canal. 



The retrograde motions of our fyftem originate either from 

 defect of ftimulus, or from defect of irritability. Thus ficknefs 

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

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

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

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

 opium, or food, relieves licknefs. 



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, becaufe 

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

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

 any additional itimulus. 



When the longitudinal mufcles are fatigued by long action, or 

 are habitually weaker than natural, the antagonift mufcles re- 

 place the limb by ft retching 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 mufcles 

 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 ftimulated, 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 circumftances, 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 difeales, fee Sect. 

 XXIX. 1 1. 5. 



The fluids difgorged by the retrograde motions of the various 

 vafcular mufcles may be diftinguiihed, 1. From thofe, which 

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



of 



