270 RETROGRADE SECT. XXIX. 11. 6. 



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

 have been accultotned to fucceffive adtions : hence when one 

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

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

 tion falls fucceflively into retrograde action , and fo on through* 

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



6' But as the retrograde motions of the ftomach, cefophagus, 

 and fauces in vomiting are, as it were, apparent to the eye 5 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 (hip ; all which originate from aflb- 

 ciation, or fympathy. See Seel- XX. on Vertigo. 



But when the ftomach is fubjedted to a lefs ftimulus than is 

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

 its motions become diilurbed, as in hunger ; fid! pain is produ- 

 ced, then ficknefs, and ai 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 ftomach do not occur till after 

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

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

 tioned above, the periftaltic motions become tremulous, and at 

 length retrograde i 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 itrong bitters, or metallic falts, are taken 

 into the ftomach, they quickly induce vomiting ; though all 

 thefe in lefs dofes excite the ftomach into more energetic acHon, 

 and ftrengthen the digeftion j as the flowers of chamomile, and 

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

 the ftomach will no; long be obedient to a ftimulus fo much 

 greater than is natural ; but its action becomes firft tremulous 

 and then retrograde. 



7. When the motions of any veflels become retrograde, lefs 

 heat of the body is produced ; for in paroxyfms of vomiting, of 

 hyiteric affecYions, of diabetes, of afthma, the extremities of the 

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

 arile from the debility of the parts in adHon , for an increafe of 

 mufcuiar adlion is always attended with increafe of heat. 



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

 defect of irritability, as (hewn above, the method of cure is eafily 



deduced ; 



