PECULIARLY MODIFIED RESPIRATORY MOVEMENTS. 249 



voluntarily or reflexly; in the latter case, it can be controlled by the will only to 

 a limited extent. 



[Causes. A cough may be discharged rcjlexly from a large number of surfaces. 

 (1) A draught of cold air striking the skin, especially of the upper part of the 

 body. (2) More frequently it is discharged from the respiratory mucous mem- 

 brane, especially of the larynx, the sensory branches of the vagus and the superior 

 laryngeal nerve being the afferent nerves. (3) Sometimes an offending body, such 

 as a pea in the external auditory meatus gives rise to coughing, the afferent nerve 

 being the auricular branch of the vagus. (4) There seems to be no doubt that 

 there may be a "gastric cough," especially in cases of indigestion, produced by 

 stimulation of the gastric branches of the vagus.] 



(2.) Hawking, or clearing the throat. An expiratory current is forced in a 

 continuous stream through the narrow space between the root of the tongue and 

 the depressed soft palate, in order to assist in the removal of foreign bodies. 

 When the act is carried out periodically the closed glottis is suddenly forced open, 

 and it is comparable to a voluntary gentle cough. This act can only be produced 

 voluntarily. 



(3.) Sneezing consists in a sudden violent expiratory blast through the nose, 

 for the removal of mucus or foreign bodies (the mouth being rarely open) after a 

 simple or repeated spasm-like inspiration the glottis remaining open. It is 

 usually caused reflexly by stimulation of sensory nerve-fibres of the nose [nasal 

 branch of the fifth nerve], or by sudden exposure to a bright light (Cassius 

 Felix, A.D. 97) [the afferent nerve is the optic]. This reflex act may be interfered 

 with to a certain extent, or even prevented, by stimulation of sensor y nerves, 

 firmly compressing the nose \vhere the nasal nerve issues. The continued use of 

 sternutatories, as in persons who take snuff, dulls the sensory nerves, so that they 

 no louger act when stimulated reflexly. 



(4.) Snoring occurs during respiration through the open mouth, whereby the 

 inspiratory and expiratory stream of air throws the uvula and soft palate into 

 vibration. It is involuntary, and usually occurs during sleep, but it may be 

 produced voluntarily. 



(5.) Gargling consists in the slow passage of the expiratory air-current in the 

 form of bubbles through a fluid lying between the tongue and the soft palate, 

 when the head is held backwards. It is a voluntary act. 



(6.) Crying, caused by emotional conditions, consists in short, deep 

 inspirations, long expirations with the glottis narrowed, relaxed facial and jaw 

 muscles, secretion of tears, often combined with plaintive inarticulate expressions. 

 When crying is long continued, sudden and spasmodic involuntary contractions 

 of the diaphragm occur, which cause the inspiratory sounds in the pharynx and 

 larynx known as sobbing. This is an involuntary act. 



(7.) Sighing is a prolonged inspiration, usually combined with a plaintive 

 sound often caused involuntarily, owing to painful or unpleasant recollections. 



(8.) Laughing is due to short, rapid expiratory blasts through the tense vocal 

 cords which cause a clear tone, and there are characteristic inarticulate sounds in 

 the larynx, with vibrations of the soft palate. The mouth is usually open, and 

 the countenance has a characteristic expression, owing to the action of the M. 

 zygomaticus major. It is usually involuntary, and can ouly be suppressed, to a 

 certain degree, by the will (by forcibly closing the mouth and stopping respiration). 



(9.) Yawning is a prolonged, deep inspiration occurring after successive 

 attempts at numerous inspirations the mouth, fauces, and glottis being wide 

 open ; expiration shorter both acts often accompanied by prolonged character- 

 istic sounds. It is quite involuntary, and is usually excited by drowsiness or 

 ennui. 



[(10.) HicCOUgh is due to a spasmodic involuntary contraction of the diaphragm, 

 causing an inspiration, which is arrested by the sudden closure of the glottis, so 



