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accompanied by groans, becomes necessary, as the motions of respiration 

 rendered progressively slower, are no longer sufficient to dilate the pul- 

 monary tissue. 



Sobbing differs from sighing, merely in this, that though the expiration 

 is long, it is interrupted, that is, divided into distinct periods. 



Yawning is effected in the same manner ; it is the certain sign of ennui, 

 a disagreeable affection, which, to use the expression of Brown, may be 

 considered as debilitating or asthenic. The fatigued inspiratory muscles 

 have some difficulty in dilating the chest, the contracted lungs are not 

 easily penetrated by the blood which stagnates in the right cavities of the 

 heart, and produces an uneasy sensation, which is put an end to by along 

 and deep inspiration ; the admission of a considerable quantity of air is 

 facilitated by opening the mouth widely, by the separation of both jaws. 

 One yawns at the approach of sleep, because the agents of inspiration, 

 being gradually debilitated, require to be roused at intervals. One is, 

 likewise, apt to yawn on waking, that the muscles of the chest may be 

 set for respiration, which is always slower and deeper, during sleep. It 

 is for the same reason, that all animals yawn on waking, that the muscles 

 may be prepared for the contractions which the motions of respiration 

 require. The crowing of the cock and the flapping of his wings seem to 

 answer, the same purpose. It is in consequence of the same necessity, 

 that the numerous tribes of birds in our groves, on the rising of the sun, 

 warble, and fill the air with harmonious sounds. A poet then fancies he 

 hears the joyous hymn, by which the feathered throngs greet the return 

 of the God of light. 



While gaping lasts, the conception of sounds is less distinct, the air, as 

 it enters the mouth, rushes along the eustachian tubes into the tympanum, 

 and the membrane is acted upon in a different direction. The recollec- 

 tion of the relief attending the deep inspiration which constitute gaping, 

 the recollection of the grateful sensation which follows the oppression 

 that was felt before, involuntarily leads us to repeat this act whenever 

 we see any one yawning. 



Sneezing consists in a violent and forcible expiration, during which the 

 air, expelled with considerable rapidity, strikes against the tortuous nasal 

 passages, and occasions a remarkable noise. The irritation of the pitui- 

 tary membrane determines, by sympathy, this truly convulsive effort of 

 the pectoral muscles, and particularly of the diaphragm. 



Coughing bears a considerable resemblance to sneezing, and differs 

 from it, only in the shorter period of duration and the greater frequency 

 of the expirations ; and as in sneezing, the air sweeps along the surface 

 of the pituitary membrane, and clears it of the mucus which may be ly- 

 ing upon it, so the air, when we cough, carries along with it the mucus 

 contained in the bronchiae, in the trachea and which we spit up. The 

 violent cough, at the beginning of a pulmonary catarrh, the sneezing 

 which attends coryza, show that the functions of the animal economy 

 are not directed by an intelligent principle, for such an archseus could not 

 mistake, in such a manner, the means of putting a stop to the disease, 

 and would not call forth actions which instead of removing the irritation 

 and inflammation already existing, can only aggravate them. 



Laughing is but a succession of very short and very frequent expira- 

 tions. In hiccup, the air is forcibly inspired, enters the larynx with dif- 

 ficulty, on account of the spasmodic constriction of the glottis; it is then 

 expelled rapidly, and striking against the sides of that aperture, occasions 

 the particular noise attending it. 



