150 PHYSIOLOGY. 



part of the system. We will not pretend to explain completely 

 what is the foundation of this singular connexion ; but we can 

 observe this, that no internal part of the system is so remark- 

 ably an organ of sensation as the stomach, that it not only ex- 

 presses its own different conditions with regard to fulness, emp- 

 tiness, the acrimony of the matter which it contains, &c. but 

 the general state of the system also, as more full or empty. 

 The stomach must, therefore, have a more particular power in 

 affecting the brain, as it is from the organs of sense that the 

 beginning of all the motions of the system arises. When treat- 

 ing of the impressions of sensation as the causes of waking 

 (CXXIX.), I mentioned analogous impressions, and the chief 

 circumstance was their operation upon the stomach, which is 

 sometimes with, and sometimes without sensation. This action 

 is not so constant as that of the heart and organs of respiration, 

 but differs in this, that it is subject to a very great variety ; for 

 the difference between the action of a full stomach, and one al- 

 most empty, is very considerable ; and it must be exposed to all 

 the variety of intermediate states between its strongest and 

 weakest action. For this it depends upon the energy of the 

 brain, which indeed constantly operates, but must admit of some 

 inequality, and must more especially affect this organ." 



" We must not omit taking notice of one very general case 

 of very great influence in almost the whole of the doctrines of 

 the materia medica, as this particular sympathy is concerned in 

 the operation of the most part of medicines, and explains the 

 operation of many which is otherwise difficult to be understood. 



" This is the operation of medicines upon the stomach, from 

 which motions are often propagated to almost every distant 

 part of the human body, and peculiar effects produced in those 

 parts, whilst the medicine itself is only in contact with the stomach. 



" The stomach is the part by which the most part of substances 

 introduced into the interior parts of the body generally pass ; 

 and it is endued with a peculiar sensibility, which renders 

 it ready to be affected by every substance entering into it that 

 is active with respect to the human body. Every thing, 

 therefore, of this kind introduced into the stomach, operates al- 

 most always there, and for the most part only there. It is now, 



