CULSS IV. 1. 1. OF ASSOCIATION. 367 



motions of the stomach and oesophagus are induced, and which 

 it is of consequence to distinguish from each other. The first 

 is the mode above described, where an effort is made to dislodge 

 something, which stimulates the stomach into disagreeable sen- 

 sation; and which is returned by repeated exertions; as when 

 a nauseous drug is taken into the mouth, or a bit of sand falls 

 into the eye, or a drop of waier into the wind-pipe. In this 

 the peristaltic motions of the stomach are first stopped, and then 

 reverted by painful sensation; and the abdominal muscles and di- 

 aphragm by repeated efforts become associated with them. Now 

 as less sensorial power is expended on the retrograde actions of 

 the stomach, and of the lymphatics, which open their mouths 

 on its surface, than by their natural motions, an accumulation 

 of sensorial power in the fibres of the stomach follows the exhi- 

 bition of an emetic, and on that account an emetic will some- 

 times stop a spontaneous vomiting which was owing to sensorial 

 deficiency. See Sect. XXXV. 1. 3. and Art. V. 2. 1. 



As bitters and metallic salts, exhibited in small doses, stimu- 

 late the stomach into greater action, as appears by their increas- 

 ing the power of digestion, and yet become emetic, when given 

 in larger doses; one might suspect that they became emetic 

 by inducing debility, and consequent retrograde actions of the 

 stomach, by their previously exhausting the sensorial power by 

 their great stimulus; which might be effected in a moment 

 without producing pain, and in consequence without our per- 

 ceiving it. But on the contrary, there does not in general ap- 

 pear on the exhibition of emetics to be any previous exhaustion 

 of sensorial power; because there is evidently an accumulation 

 of it during the sickness, as appears from the digestion being 

 stronger afterwards; and from the increased action of the cellu- 

 lar and cutaneous absorbents during its operation. See Art. V. 

 2. 1. 



Another mode by which vomiting is induced, is owing to de- 

 bility or deficiency of sensorial power, from the previous ex- 

 haustion of it; as on the day after intoxication, or which occurs 

 in people enfeebled with the gout, and in dropsy, and in some 

 fevers with debility. In these, when the vomiting ceases, there 

 is no appearance of accumulation of sensorial power, as the di- 

 gestion still remains weak and imperfect. 



Another mode by which sickness of vomiting is induced, is 

 by defect of stimulus, as in great hunger; and in those, who have 

 been habituated to spice and spirit with their meals, who are 

 liable to be sick after taking food without these additional stimuli. 

 Other means of inducing sickness by vertigo, or by nauseous 

 ideas, will be mentioned below. 



