SEC. 9. MODIFIED KESPIEATORY MOVEMENTS. 



318. The respiratory mechanism with its adjuncts, in 

 addition to its respiratory function, becomes of service, especially 

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

 respiratory 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 pecul- 

 iarly modihed and more or less complicated respiratory move- 

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

 ends which are not distinctly respiratory. They are all essen- 

 tially reflex in character, the stimulus determining each move- 

 ment, 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. 



511 



