346 MANUAL OF PHYSIOLOGY. 



Sighing is a long slow inspiration, quickly followed by a cor- 

 responding expiration. 



Yawning is a very long deep inspiration, completely filling the 

 chest. It is accompanied by a peculiar depression of the lower 

 jaw, wide open mouth, facial movements, and commonly stretch- 

 ing of the limbs. 



Hiccough is a sudden inspiratory spasm chiefly of the dia- 

 phragm, the entrance of the air being suddenly checked by the 

 sudden closure of the glottis. 



