CH. II.] EXTERNAL SENSATIONS. 41 



it ; although the external impression that takes place at the same 

 time, betrays itself by animal actions, namely, contraction of 

 the stomach, as is proved by the rumbling of the flatus. But 

 the transmission of the external impression to the brain is 

 prevented in the natural state, or state of health, in a way which 

 requires a copious elucidation. 



48. iv. It is incontrovertible, that many nerves, although 

 sensitive, are mainly appropriated to certain special movements ; 

 and that the external impressions necessary thereto, are seldom 

 or never transmitted to the brain, or only those of a certain 

 kind ; but that, for the most part, it is their normal condition 

 to remain in the nerve. The nerves of the stomach, intestines, 

 and heart, illustrate this point. Food which gives rise to a 

 strong sensation in the mouth, causes no sensation whatever 

 when passed into the stomach. Whether it be bitter, sweet, 

 or salt, it is the same in the stomach. Yet the stomach is 

 more amply supplied with nerves than most other viscera, and 

 these are highly sensitive to other impressions, as those of acrid 

 poisons, for example, and consequently quite susceptible of ex- 

 ternal impressions. As food comes into contact with them as 

 certainly as poisons, and excites an external impression, which 

 undeniably develops the animal movements of digestion that 

 result from the contact, it necessarily follows, that the external 

 impressions on these nerves are not generally transmitted to 

 the brain, but are lost in the mechanical machines, to the 

 movement of which they are specially appropriate. An 

 acridity in the stomach will be felt little, if at all ; but if it be 

 in the mouth, it almost suffocates us, and bites the tongue ; on 

 the other hand, it will excite a gastric spasm in the gastric nerves 

 by its external impression. The heart is abundantly supplied 

 with nerves, and remarkably sensitive. The impression of the 

 blood flowing through it excites its movement, which, even 

 when it has ceased, can be renewed by the injection of warm 

 fluids, and yet the mind feels nothing of this external impression. 

 The special destiny of these nerves is to excite the motion of 

 the heart, which, according to the views of all physicians, is 

 vital and not mechanical in its nature. It is so little necessary 

 that the external impression made on the nerves which move it 

 be felt, that motion can be re-excited in a heart detached from 

 the body by an external impression on the terminating fibrils 



