Physiology of Speech. 9" 



by the very same parts ; and we shall thus be better enabled to 

 deduce the functions of some of these parts, or to confirm the 

 conclusions we may draw, relative to the nature of these func- 

 tions, as obtaining in the mechanism of speech. 



I would then, in the first place, refer to the function of deglu- 

 tition, or swallowing. — In order to effect deglutition, every 

 cavity or canal with which the mouth communicates must be 

 accurately closed, with the exception of the pharynx and gullet, 

 along which the substance swallowed is propelled, whilst the 

 various muscles by which deglutition is effected are called into 

 action : — the mouth is thus closed in front by the lips, the wind- 

 pipe is closed and accurately secured by a little valve-like body, 

 called the epiglottis ; and the posterior openings of the nostrils 

 are closed by the pendulous vail of the palate being drawn up- 

 wards and accurately applied to them. Thus is the cavity of the 

 mouth completely shut, and excluded from its communications 

 with the open air, or with the lungs. And if, from laughing or 

 inadvertency, or from a defective action of the parts, as in palsy, 

 any one of these functions be not adequately performed, the 

 consequences are well known ; the substances which ought to 

 have passed down the pharynx and oesophagus, escape out of 

 the mouth ; or into the windpipe, inducing the most distressing 

 coughing; or in some instances, though more rarely, into the 

 nostrils. 



I notice, in the second place, a function of the mouth equally 

 different from deglutition and articulation. It is performed in 

 the act of sucking, and in that of blowing the bl<>w-pipe. 

 The first of these acts implies a diminished, the second an increas- 

 ed, elasticity and pressure, with regard to the air contained in 

 the mouth ; and yet, during the continuance of these acts, we ^re 

 enabled to breathe freely and uninterruptedly through the nos- 

 trils, whilst the cavity of the mouth is complete, and its posterior 

 aperture closed by means of the pendulous vail of the palate, the 

 windpipe and nostrils communicate freely behind that vail. 



In the act of deghitition, then, the nostrils and the windpipe are 

 accurately closed by their respective valvea* In the acts just 



