382 OF RESPIRATION. 



ments of respiration. Hence this action is only occasionally connected with 

 mental emotion. Yawning is a still deeper inspiration, which is accompanied 

 by a kind of spasmodic contraction of the depressors of the lower jaw. and 

 also by a very great elevation of the ribs, in which the scapulse partake. 

 The purely voluntary character of this movement is sometimes seen, in a 

 remarkable manner in cases of palsy ; in which the patient cannot raise his 

 shoulder by an effort of the will, but does so in the act of ya wiring. Never- 

 theless this act may be performed by the will, though not completely; and is 

 one that is particularly excited by an involuntary tendency to imitation, as 

 every one must have experienced who has ever been in company with a set 

 of vawners. Sobbing is the consequence of a series of short convulsive con- 

 tractions of the diaphragm ; and it is usually accompanied by a closure of the 

 glottis, so that no air really enters. In Hiccough, the same convulsive respi- 

 ratory movement occurs, and the glottis closes suddenly in the midst of it ; 

 the sound is occasioned by the impulse of the column of air in motion against 

 the glottis. In Laughing, a precisely reverse action takes place ; the muscles 

 of expiration are in convulsive movement, more or less violent, and send out 

 the breath in a series of jerks, the glottis being open. This sometimes goes 

 on, until the diaphragm is more arched, and the chest is more completely 

 emptied of air, than it could be by an ordinary movement of expiration. 

 The act of Crying, though occasioned by a contrary emotion, is, so far as the 

 respiration is concerned, very nearly the same as the last. Every one knows 

 the effect of mixed emotions, in producing an expression of them which is 

 " between a laugh and a cry."- -The greater part of the preceding movements 

 seem to belong as much to the consensual or to the emotional, as to the e.rc I to- 

 motor group of actions ; for whilst they are sometimes the result of peculiar 

 states of the respiratory organs, or of the bodily system in general, they may 

 also be called forth by influences which operate directly through the senses, 

 or which excite the emotions. Thus, whilst Sighing and Yawning often 

 occur as simple results of deficient aeration, they may be brought on, the 

 former by a depressed state of the feelings, the latter by the mere sight of 

 the act in another person. The actions of Laughter and Crying seem never 

 to originate in the respiratory system ; but to be always either expressions of 

 the emotions, or simple results of sensations, as when crying arises from the 

 sense of pain, and laughter from that of tickling. The origin of the act of 

 Hiccough does not seem very clear; but the movement is probably of a purely 

 reflex nature. 



304. The purposes of the acts of Coughing and Sneezing are, in both in- 

 stances, to expel substances from the air-passages, which are sources of irrita- 

 tion there; and this is accomplished in both, by a violent expiratory effort, 

 which sends forth a blast of air from the lungs. Coughing occurs when the 

 source of irritation is situated at the back of the mouth, in the glottis, trachea, 

 or bronchial tubes. The irritation may be produced by acrid vapors, or by 

 liquids or solids, that have found their way into these passages; or by secre- 

 tions which have been poured into them in unusual quantity, as the result of 

 disease ; or by the simple entrance of air (especially if cold), when the mem- 

 brane is in a peculiarly irritable state. Any of these causes may produce an 

 impression upon the excitor fibres of the superior 1 and inferior 2 laryngeal 

 branches of the Pneumogastrics, which, being conveyed to the Medulla Ob- 

 longata, gives rise to the transmission of a motor impulse to the several 

 muscles, that combines them in an act of expiration. The act of coughing 

 consists, 1st, in a long inspiration, which fills the lungs; 2d, in the closure 



1 Sec Knxcnthal, Die Atliombewpgun^pn, 18G2; and Reichert's Archiv, 1844. 

 * liurkliart, Pflilger's Aruhiv, Bd. i, p. 107. 



