ON LAUGHTER. 353 



is the reliabilitatioD of function, the rebound to increased metabolism. 

 This may also explain the easily- excited laugh of those attendants at 

 a funeral or solemn ceremony where the grief is not too intense. 

 Any foolish stimulus may cause the metabolic rebound. A friend 

 of mine once attended an execution. The morning sun was excluded, 

 the shadow and damp of prison walls were everywhere, the usual 

 crowd of curiosity-mongers was present. Upon regaining the open 

 air and sunlight the major part of the crowd burst out laughing with 

 no other external stimulus than the exuberant sunligrht. 



The mechanics of laughter would also have to take into account 

 the important influence exercised by the diaphragm, the muscular 

 walls of the stomach and glandular activity in the various degrees of 

 the laugh. 



Sully mentions the scratching of the head during a state of men- 

 tal irritation as a well-known instance of the transference of expres- 

 sive movement from one state of feeling to another, a la Darwin and 

 AVundt. Lauder Brunton explains this habit of the English rustic 

 and similar ones, such as pulling the mustache or beard, or the Ger- 

 man habit of slapping the side of the nose with the finger, as a stim- 

 ulation of some branches of the fifth nerve, thereby causing local 

 dilatation of the cerebral vessels and an added ability to carry on a 

 line of thought. In a similar manner the gustatory branches and 

 the buccal branches of the fifth nerve are stimulated by taking some- 

 thing that has a strong taste, such as brandied cherries. In rural 

 regions peppermint candy is the open sesame of wakefulness in this 

 line. Sucking and chewing and sipping are stimulants greatly 

 increasing the flow of blood through the carotids, as has been deter- 

 mined by experiment. Certain elements of the smoking habit have 

 their raison d''etre in activity of this sort. The habit many boys 

 have of spitting on their hands and then of rubbing them together 

 before taking a leap is based on the fact that thereby they 

 obtain a sensori-muscular stimulation. Many mental and bodily 

 automatisms usually explained by reference to some general principles 

 such as inhibition ought to be reexamined with the view of ascer- 

 taining the special causation in question. 



