Ct ASS I. 3.1. OF IRRITATION. 131 



ORDO III. 



Retrograde Irritative Motions. 



GENUS I. 

 Of the Alimentary Canal. 



THE retrograde motions of our system originate either from 

 defect of stimulus, or from defect of irritability. Thus sickness 

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

 from ipecacuanha, in which last case it would seem, that the 

 sickness was induced after the violence of the stimulus was abat- 

 ed, and the consequent torpor had succeeded. "Hence, spice, 

 opium, or food, relieves sickness. 



The globus hystericus, salivation, diabetes, and other inver- 

 sions of motion attending hysteric paroxysms, seem to depend on 

 the want of irritability of those parts of the body, because they 

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

 relieved by wine, opium, steel, and ilesh diet; that is, by any ad- 

 ditional stimulus. 



When the longitudinal muscles are fatigued by long action, or 

 are habitually weaker than natural, the antagonist muscles re- 

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

 these muscles have had their actions associated in synchronous 

 tribes, their actions cease together. But as the hollow muscles 

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

 trains; wh?n one ring is fatigued from its too great debility, and 

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

 from its association in train falls into retrograde action. Which 

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

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

 Now as these hollow muscles are perpetually stimulated, these 

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

 nal muscles, which are generally excited only by volition. 

 Whence the retrograde motions of hollow muscles depend on 

 two circumstances, in which they differ from the longitudinal 

 muscles, namely, their motions being associated in trains, and 

 their being subject to perpetual stimulus. For further elucida- 

 tion of the cause of this curious source of diseases, see Sect. 

 XXIX. 11.5. 



The fluids disgorged by the retrograde motions of the various 

 vascular muscles may be distinguished, 1. From those which 

 are produced by secretion, by their not being attended by increase 



