152 PHYSIOLOGY. 



upon the sensible and irritable parts of the stomach. This I con- 

 ceive to be the case of opiates and of most other narcotic powers, 

 whose substance is known to remain in the stomach long after 

 they have discovered their effects in the most distant parts of. 

 the system. 



"Fourthly: If there are medicines supposed to act only when 

 they come in contact with the parts they are supposed to act 

 upon, and if a certain quantity is necessary to be applied to 

 these parts ; and, further, if such medicines are either thrown 

 into the stomach in small quantity, or are of a nature to be. 

 slowly dissolved there, so that they cannot be supposed in suffi- 

 cient quantity to come in contact with the parts they are des- 

 tined to act upon, whilst however their effects appear in these 

 parts, it must, I think, be concluded, that these effects depend 

 entirely upon the operation of these medicines upon the stomach. 

 This, if I mistake not, applies to the case of most vegetable 

 astringents, and perhaps to the fossil also, whose effects, and 

 especially their sudden effects, upon distant parts of the system, 

 can only be accounted for by their operation upon the stomach. 



" Fifthly : Another circumstance leading us to suppose that 

 medicines act immediately upon the stomach, and by their oper- 

 ation there, affect the rest of the system, is the consideration of 

 all these cases where they affect the system very generally, 

 while, at the same time, they act both suddenly and in small 

 quantity, and therefore in circumstances which cannot allow us 

 to suppose that they are conveyed in substance to the parts in 

 which their effects appear. Thus, as has been above observed, 

 medicines which act very generally upon the nervous system, or 

 upon the particular parts of it remote from the stomach, cannot 

 be supposed to be transferred in substance to the whole, or even 

 to the particular parts of that system, and therefore must ne- 

 cessarily be supposed to act in the stomach only. Not only, 

 however, with respect to the nervous system, but also with re- 

 spect to the sanguiferous, any very general effects produced 

 there, as, for example, a sweating excited universally over the 

 whole body, can be produced no otherwise by internal medicines 

 excepting by such as act on the stomach, and from thence com- 

 municate a stimulus to the heart and arteries. In many cases 

 of increased evacuations, it is indeed pretty evident that the 



