SEC. 10. MODIFIED RESPIRATORY MOVEMENTS. 



391. The respiratory mechanism with its adjuncts, in ad- 

 dition to its respiratory function, becomes of service, especially in 

 the case of man, as a means of expressing emotions. The respi- 

 ratory column of air, moreover, in its exit from the chest, is 

 frequently made use of in a mechanical way to expel bodies from 

 the upper air-passages. Hence arise a number of peculiarly 

 modified and more or less complicated respiratory movements, 

 sighing, coughing, laughter, &c. adapted to secure special ends 

 which are not distinctly respiratory. They are all essentially 

 reflex in character, the stimulus determining each movement, 

 sometimes affecting a peripheral afferent nerve as in the case 

 of coughing, sometimes working through the higher parts of the 

 brain as in laughter and crying, sometimes possibly, as in yawning 

 and sighing, acting on the respiratory centre itself. Like the 

 simple respiratory act, they may with more or less success be 

 carried out by a direct effort of the will. 



Sighing is a deep and long-drawn inspiration, chiefly through 

 the nose, followed by a somewhat shorter, but correspondingly 

 large expiration. 



Yawning is similarly a deep inspiration, deeper and longer 

 continued than a sigh, drawn through the widely open mouth, 

 and accompanied by a peculiar depression of the lower jaw and 

 frequently by an elevation of the shoulders. 



Hiccough consists in a sudden inspiratory contraction of the 

 diaphragm, in the course of which the glottis suddenly closes, so 

 that the further entrance of air into the chest is prevented, while 

 the impulse of the column of air just entering, as it strikes upon 

 the closed glottis, gives rise to a well-known accompanying sound. 

 The afferent impulses of the reflex act are conveyed by the gastric 

 branches of the vagus. The closure of the glottis is carried out by 

 means of the inferior laryngeal nerve. See Voice. 



In sobbing a series of similar convulsive inspirations follow each 

 other slowly, the glottis being closed earlier than in the case of 

 hiccough, so that little or no air enters into the chest. 



