L98 THE PHYSIOLOGY OF LAUGHTER. 



motor nerves, and so cause muscular contractions ; or they 

 may pass on the excitement to nerves which supply the vis- 

 cera, and may so stimulate one or more of these. 



For simplicity's sake, I have described these as alterna- 

 tive routes, one or other of which any current of nerve- 

 force must take ; thereby, as it may be thought, implying 

 that such current will be exclusively confined to some one 

 of them. But this is by no means the case. Rarely, if 

 ever, does it happen that a state of nervous tension, present 

 to consciousness as a feeling, expends itself in one direction 

 only. Very generally it may be observed to expend itself 

 in two ; and it is probable that the discharge is never abso- 

 lutely absent from any one of the three. There is, how- 

 ever, variety in the proportions in which the discharge is 

 divided among these different channels under different cir- 

 cumstances. In a man whose fear impels him to run, the 

 mental tension generated is only in part transformed into a 

 muscular stimulus : there is a surplus which causes a rapid 

 current of ideas. An agreeable state of feeling produced, 

 say by praise, is not wholly used up in arousing the suc- 

 ceeding phase of the feeling, and the new ideas appropriate 

 to it ; but a certain portion overflows into the visceral ner- 

 vous system, increasing the action of the heart, and proba- 

 bly facilitating digestion. And here we come upon a class 

 of considerations and facts which open the way to a solu- 

 tion of our special problem. 



For starting with the unquestionable truth, that at any 

 moment the existing quantity of liberated nerve-force, 

 which in an inscrutable way produces in us the state we 

 call feeling, must expend itself in some direction — must 

 generate an equivalent manifestation of force somewhere — 

 it clearly follows that, if of the several channels it may 

 take, one is wholly or partially closed, more must be taken 

 by the others ; or that if two are closed, the discharge 

 along the remaining one must be more intense ; and that, 



