INFLUENCE OF THE BRAIN ON HEALTH. 253 



I have already had frequent occasion to notice the 

 direct influence exercised by the mind and brain 

 over all the bodily functions, and over the general 

 health. As the subject is an important one, and has 

 not received all the attention which it deserves, it 

 may be proper, before concluding, to offer a few 

 remarks on it, 



The nervous fluid or influence presents many 

 phenomena allied to those of electricity, but its real 

 flature is not yet known. All that can be said is, that 

 it is an influence of a peculiar kind, originating in the 

 Jbrain and nervous system ; and that, like the blood, 

 it is essential to the vital action of every animal 

 organ. When I move the hand in writing, the 

 muscles of the arm are called into play by an influ- 

 ence transmitted to them from the brain, by means 

 of the soft white cords called nerves. This stimu^ 

 lus is so indispensable, that if the communication 

 between the brain and the muscles be cut off, by 

 dividing or tying the nerve, no effort of the mind 

 will longer suffice to excite them to action* In like 

 manner, if the nerves of the lungs and stomach be 

 cut through, so as to interrupt the flow of nervous in- 

 fluence, respiration and digestion will cease, although 

 in every other respect their respective organs re- 

 main uninjured* 



Changes in the quality Or amount of the nervous 

 influence transmitted from the brain to any organ 

 have thus a direct power of modifying its function. 

 If, from a peculiar state of the brain, the nervous 

 influence sent to the stomach be impaired, the tone 

 of that organ will be also impaired, and digestion 

 become imperfect ; whereas if, in consequence of 

 pleasing excitement, the nervous stimulus be in- 

 creased, a corresponding activity will be com- 

 municated to the stomach, and digestion will be 

 facilitated, as is experienced after a dinner In 

 pleasant society. But if, by a violent burst of pas* 

 or grief, the brain be inordinately excited, $0 

 V 



