s 7 o RETROGRADE Sect. XXIX. u.& 



propel a fluid along their cavities, are afibciated in trains, which 

 have been accuflomed to fucceffive actions : hence when one 

 ring of fuch a mufcle is fatigued from its too great debility, and 

 is brought into retrograde aclion, the next ring from its aflbcia- 

 tion falls fucceflively into retrograde aclion ; and fo on through- 

 out the whole canal. Gee Seel:. XXV. 6. 



6. But as the retrograde motions of the ftornach, cefophagus, 

 and fauces in vomiting are, as it were, apparent to the eye ; we 

 {hall confider this operation more minutely, that the fimilar op- 

 erations in the more recondite parts of our fyftem may be eafier 

 underftood. 



From certain naufeous ideas of the mind, from an ungrateful 

 tafte in the mouth, or from foetid fmells, vomiting is fometimes 

 inftantly excited ; or even from a ftroke on the head, or from 

 the vibratory motions of a fhip ; all which originate from afToci- 

 ation, or fympathy. See Seel:. XX. on Vertigo. 



But when the ftornach is fubjefced to a lefs ftimulus than is 

 natural, according to the firft law of irritation mentioned above, 

 its motions become difturbed, as in hunger ; firft pain is produ- 

 ced, then ficknefs, and at length vain efforts to vomit, as many 

 authors inform us. 



But when a great quantity of wine, or of opium, is fwallow- 

 ed, the retrograde motions of the ftornach do not occur till after 

 feveral minutes, or even hours 5 for when the power of fo ftrong 

 a ftimulus ceafes, according to the fecond law of irritation, men- 

 tioned above, the periftaltic motions become tremulous, and at 

 length retrograde ; as is well known to the drunkard, who on 

 the next morning has ficknefs and vomitings. 



When a ftill greater quantity of wine, or of opium, or when 

 naufeous vegetables, or ftrong bitters, or metallic falts, are taken 

 into the ftornach, they quickly induce vomiting ; though all 

 thefe in lefs dofes excite the ftornach into more energetic action, 

 and ftrengrhen the digeftion ; as the flowers of chamomile, and 

 the vitriol of zinc : for, according to the fourth law of irritation, 

 the ftornach wiil not long be obedient to a ftimulus fo much great- 

 er than is natural •, but its aclion becomes firft tremulous and 

 then retrograde. 



7. When the motions of any vefTels become retrograde, lefs heat 

 of the body is produced ; for in paroxyfms of vomiting, of hyf- 

 teric affections, of diabetes, of afthma, the extremities of the 

 body are cold: hence we may conclude, that thefe fymptoms 

 arife from the debility of the parts in aclion ; for an increafe of 

 mufcular action is always attended with increafe of heat. 



8. But as animal debility is owing to defect of ftimulus, or to 

 defcci o£ irritability, as fhewn above, the method of cure iseafily 



deduced ;. 



