34^ DISEASES Sect. XXXV. r. 4, 



Hence it appears, that the aft of naufea or vomiting expends 

 lefs fenforial power than the ufual periftaltic motions of the 

 ftomach in the digeftion of our aliment ; and that hence there 

 is a greater quantity of fenforial power becomes accumulated 

 in the fibres of the ftomach, and more of it in confequence to 

 fpare for the action of thofe parts of the fyftem, which are thus 

 affociated with the ftomach, as of the whole abforbent ferie:; of 

 vefTels, and which are at the fame time excited by their ufual 

 ftimuli. 



From this we can underftand, how after the operation of an 

 emetic the ftomach becomes more irritable and fenfible to the 

 ilimulus, and the pleafure of food ; fince as the fenforial power 

 becomes accumulated during the naufea and vomiting, the digef- 

 tive power is afterwards exerted more forcibly for a time. It 

 fliould, however, be here remarked, that though vomiting is in 

 general produced by the defect of this ftimulus of pleaiurable 

 fenfation, as when a naufeous drug is administered ; yet in long- 

 continued vomiting, as in fea-ficknefs, or from habitual dram- 

 drinking, it arifes from deficiency of fenforial power, which in 

 the former cafe is exhaufted by the increafed exertion of the ir- 

 ritative ideas of vifion, and in the latter by the frequent applica- 

 tion of an unnatural ftimulus. 



4. An example of the fourth circumftance above mentioned, 

 where both the primary and fecondary parts of a train of mo- 

 tions proceed with energy lefs than natural, may be obferved in 

 the dyfpncea, which occurs in going into a very cold bath, and 

 which has been defcribed and explained in Seel:. XXXII. 3. 2. 



And by the increafed debility of the pulfations of the heart 

 and arteries during the operation of an emetic. Secondly, from 

 the flownefs and intermiihon of the pulfations of the heart from 

 the inceftant efforts to vomit occafioned by an over-dofe of dig- 

 italis. And thirdly, from the total ftoppage of the motions of 

 the heart, or death, in confequence of the torpor of the ftomach, 

 when afFecled with the commencement or cold paroxyfm of the 

 gout. See See"!. XXV. 17. 



II. 1. The primary and fecondary parts of the trains of fen- 

 fitive a-fTociation reciprocally affect each other in different man- 

 ners. 1. The increafed fenfation of the primary part may ceafe, 

 when that of the fecondary part commences. 2. The increafed 

 action of the primary part may ceafe, when that of the fecondary I 

 part commences. 3. The primary part may have increafed fen- 

 fation, and the fecondary part increafed action. 4. The pri-j 

 mary part may have increafed action, and the fecondary part in- 

 creafed fenfaticn. 



Examples of the firft mode, where the increafed fenfation of 



the 



