PHYSIOLOGY. 151 



however, well known to physicians, that the most considerable 

 instance of the sympathy mentioned above, is afforded by 

 the stomach, so connected with almost every other part of the 

 system, that motions excited there are communicated to al- 

 most every other part of the body, and produce peculiar ef- 

 fects in those parts, however distant from the stomach itself. 

 This indeed is very well known ; but that the effects of many 

 medicines which appear in other parts of the body are entirely 

 owing to an action upon the stomach, and that the most part of 

 medicines acting upon the system act immediately upon the 

 stomach only, is what has not been understood till very lately, 

 and does not seem even yet to be very generally and fully per- 

 ceived by the writers on the materia medica. It will, therefore, 

 be proper here to say in what manner this doctrine may be es- 

 tablished. 



" First : That medicines shewing considerable powers with re- 

 spect to the whole system, act especially or only on the stomach, 

 will appear from all those cases in which the effects appear soon 

 after the substance has been taken into the stomach, and before 

 they can be supposed to have gone further into the body, or to 

 have reached the mass of blood. Thus, Sir John Pringle, from 

 the sudden operation of the Peruvian bark in preventing the 

 paroxysms of intermittent fevers, properly concludes, that it can- 

 not be by its antiseptic powers with respect to the fluids, but by 

 a certain operation immediately upon the stomach. (See Dis- 

 eases of the Army, Appendix, p. xxv.) 



" Secondly : As medicines are commonly in the first place 

 applied to the stomach, so all those of volatile, active, and 

 penetrating parts, must immediately and especially act upon 

 the stomach ; and from this consideration, as well as from the 

 suddenness of their effects which commonly appear, we may con- 

 clude their action to be upon the stomach only. Accordingly, 

 I conclude that the action of the volatile alkali, and some other 

 saline substances, is upon the stomach alone, and very rarely by 

 any antiseptic powers with respect to the fluids, 



" Thirdly : Though medicines do not to the taste or smell 

 discover any volatile or active parts, yet if their effects depend 

 upon the change which they produce in the state of the nerv- 

 ous power, it is hardly to be doubted that they operate only 



