HOW WH SNEEZE, LAUGH, STAMMER, AND SIGH. 495 



state of over-irritation, and return to their normal condition. "We 

 must, however, be careful not to fall into the common error of con- 

 founding stuttering with stammering. In stuttering the process of 

 breathing is quite normal, and the defective speech arises only from 

 inaptitude in the formation of sound ; this defect of speech is, there- 

 fore, peculiar to children, idiots, and persons suffering from apoplexy. 



Sighing, which is classed by Von Meyer as an unusual form of ex- 

 piration, is better regarded as including the preceding inspiration also. 

 A sigh is in fact a long breath, and, like a gape, is an involuntary 

 spurt made to catch up with the demand for air. This is true even 

 when it arises from depressing emotion. The expiration is often the 

 more prominent part of the action, the rapidity with which the air 

 flows out being due to a sudden cessation of the activity of the expira- 

 tory muscles, which commonly regulate, by retarding, the issuing 

 stream of air. In sobbing, air is obtained by short, abrupt inspirations, 

 and the tears which overflow into the nasal cavity assist in causing 

 this air to produce sound. 



Sneezing is the simplest of the purely expiratory noises. Just as 

 the hiccough depends upon a single violent spasm during inspiration, 

 so the sneeze is due to a single violent spasm during expiration, gen- 

 erally of the abdominal muscles, but, when very violent, of the other 

 expiratory muscles also. It is a reflex action which occurs after an 

 irritation of the mucous membrane lining the air-passages of the nose, 

 and also after irritation of the optic nerve by a bright light. A few 

 slight contractions of the abdominal muscles are at first suppressed by 

 some short inspirations rapidly following each other without any in- 

 tervening expiration ; then follows a vigorous contraction of the ab- 

 dominal muscles, by means of which the stream of air is violently 

 driven out through the mouth and nose. In its passage through the 

 nose, the air produces a well-known noise, which may, however, be 

 connected with a sound produced in the vocal chords. "We recognize 

 the same peculiarity, though the action is voluntarily performed, in 

 blowing the nose. Sneezing is not an observer of times and seasons, 

 and often seems to choose the most inopportune moment for exhibiting 

 its power. In such a case the impending catastrophe may be averted 

 by pressing firmly upon some branch of the fifth nerve, say in the up- 

 per lip close under the nose. 



Coughing and laughing are also due to a spasmodic contraction of 

 the expiratory muscles. These acts differ from sneezing only in this 

 respect, that, while in the latter expiration is accomplished by a single 

 violent action, it is here characterized by a number of separate im- 

 pulses of the expiratory muscles with small intervening pauses. In 

 long-continued coughing or laughing, short inspirations, which, on ac- 

 count of their shortness and violence, often approach the verge of 

 hiccoughing, are taken between the separate expirations, and, indeed, 

 laughing after a full meal frequently leads to a fit of hiccoughs. Cough- 



