66 THE CAUSATION OF DISEASE. 



greater demand upon the rest of the body than an excessive 

 muscular system in the man. 



Woman will always be more emotional than man. The 

 emotions are grounded on the feelings, or, to speak more pre- 

 cisely, on the sensations,* and these latter originate in impres- 

 sions made upon peripheral nerve- terminations. Let c (Fig. 3) 



Fig. 3. 



filtl ^"'~ Sensory centre. 



O Sensory nerve. 



— O. Sensory nerve-ending. 



be a cortical sensory centre ; 5, its sensory nerve ; a, the peri- 

 pheral nerve-termination. An impression upon a causes a nerve 

 impulse to pass up &, and this striking upon c brings about a 

 series of molecular changes. The " material conditions " of c 

 represent the physical side of a sensation, and, so far as it is 

 possible to define the cause of a sensation, they are the cause 

 of such sensation. What may be the exact connection between 

 the material conditions, as represented by c, and the resulting 

 mental state, it is not for us here to inquire. It is enough to 

 state the simple fact that the peculiar material state of c is 

 accompanied by the mental state. This is the " explanation " 

 of all sensations : a is, as it were, the keyboard, c the pipe 

 (or series of pipes) of an organ. An impression upon the key- 

 note calls forth sound from the pipe, just as an impression upon 

 a sensory nerve-termination calls forth sensation from its sensory 

 centre. The animal body contains myriads of such sensory 

 peripheral nerve-endings, and corresponding cortical centres. 

 Impulses are continually streaming up these sensory nerves 



* The feelings include the simple sensations, and the emotions. These latter 

 are founded upon the sensations, more especially the organic sensations. 



