THE PHYSIOLOGY OF EMOTION. 275 



by action is exhausted, the energizing will be attended with propor- 

 tionate pain. 



It may be a question whether "nerve-force" is the best term to 

 apply to the condition I have spoken of. It is one which opens up the 

 many controversies which exist, and have existed, as to. the nature of 

 force, the relations of the various physical forces, and of these to the 

 forces which we see at work in living animals. While, on the one 

 hand, some shrink away from the very name of force, and will none of 

 it, as a metaphysical entity to be relegated to the schoolmen along with 

 that other metaphysical entity, the " mind " itself, on the other, it is to 

 be feared that men have imagined that the study of mental phenomena 

 ha^s, at length, attained to the rank of the exact sciences, because they 

 have placed nerve-force in the same category and correlated group as 

 light, heat, gravity, and electricity. " Animal combustion," says Mr. 

 Bain, " maintains nervous power, or a certain flow of the influence cir- 

 culating through the nerves, which circulation of influence, besides 

 reacting on the other animal processes, muscular, glandular, etc., has, 

 for its distinguishing: concomitant, the mind. The extension of the 

 correlation of force to mind, if at all competent, must be made through 

 the nerve-force, a genuine member of the correlated group." It may 

 be interesting to see in what way another distinguished philosopher 

 connects the forces of purely physical phenomena with those of life 

 and animal movement. In his work on Heat (p. 499), Prof. Tyndall 

 writes : " The grand point, permanent throughout all these considera- 

 tions, is that nothing is created. We can make no movement which is 

 not accounted for by the contemporaneous extinction of some other 

 movement. And, how complicated soever the motions of animals may 

 be, whatever may be the change which the molecules of our food 

 undergo within our bodies, the whole energy of animal life consists in 

 the falling of the atoms of carbon and hydrogen and nitrogen from 

 the high level which they occupy in the food to the low level which 

 they occupy when they quit the body. But what has enabled the 

 carbon and the hydrogen to fall ? What first raised them to the level 

 which rendered the fall possible ? We have already learned that it is 

 the sun. It is at his cost that animal heat is produced and animal mo- 

 tion accomplished." 



When I speak of there being in each nerve cell or centre a condi- 

 tion, varying within certain limits, according to which it is capable of 

 energizing more or less readily and pleasantly, I am far from intending 

 to convey a not ion of any metaphysical entity, even if I use the term 

 " nerve-force." It is not possible to separate this force in kind from 

 that which is the special property of the cell. Each cell, as it lives 

 its life in our bodily organization, as it grows to maturity, and fades 

 in its decay, separates and selects from the blood, by a moleculnr met- 

 amorphosis, that which it requires for its function as an idea-cell, a 

 hearing, or a sight cell, but it separates it in varying quantity and 



