290 VARIOUS MOVEMENTS CONNECTED WITH RESPIRATION. 



strongly, and which, has prevented our feeling the insufficiency 

 of the ordinary respiratory movements. 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 muscles of the jaw, and also 

 by a very great elevation of the ribs, in which the shoulders 

 and arms partake. The purely involuntary 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 yawning. Never- 

 theless the action may be performed by the will, though not 

 completely ; and it 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 

 yawners. Sobbing is the consequence of a series of short 

 convulsive contractions of the diaphragm ; and it is usually 

 accompanied by a closure of the glottis, so that no air really 

 enters. In Hiccup, the same convulsive inspiratory movement 

 occurs, the glottis closing suddenly in the midst of it ; and 

 the sound is occasioned by the impulse of the column ol 

 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 some- 

 times goes on until the diaphragm is more arched, and the 

 chest 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. We all know the effect 

 of mixed emotions in producing something " between a laugh 

 and a cry." 



342. The purposes of the acts of coughing and sneezing are, 

 in both instances, to expel substances from the air-passages, 

 which are sources of irritation 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 

 trachea, or bronchial tubes. The irritation may be produced 

 by acrid vapours, or by liquids or solids that have found 

 their way into these passages, or by secretions which have 

 been poured into them in unusual quantity as the result of 



