THE DIGESTIVE SYSTEM. ll^" 



between the incisor teeth and tlie cartilaginons pad in the 

 mouth, is moderately chewed by the molar teeth, being replaced 

 between them by the action of the tongue and cheeks, it is then 

 formed into a bolns, thoroughly saturated witli the saliva, and 

 convej^ed by the tongue back into a poiich situated at the super- 

 ior extremity of the gullet, called the pharynx. 



The pharynx is lined with mucous membrane the same as 

 the moxith. It is rirtually a mucous lined muscular box, the 

 contraction of the sides being the means by which the food is 

 forced into the gullet, which scientifically is termed the oeso- 

 phagus, and is the tube connecting the mouth with the stomach. 

 Immediately imder the pharynx we find a cartilaginous box, 

 termed the larynx, forming the entrance to the windpipe, or 

 trachea. The food passes into the gullet, over the larynx, from 

 which, however, it is prevented from entering by a triangular 

 lid composed of cartilage and termed the epiglottis, which is 

 forced down, effectually closing the entrance to the larynx. 

 Directly the food has passed over the larynx, the epiglottis as- 

 sumes an upright f)osition, freeing the entrance to the larynx 

 and permitting the entrance of air for the purpose of respiration. 

 The food after leaving the pharynx passes into the gullet. This 

 is composed of involuntary muscular fibres, and the bolus, acting 

 as an irritant, causes these muscles to contract, the fibres run- 

 ning lengthwise with the tube, draw it up, shortening the distance 

 between the stomach and the mouth, while the contraction of 

 the circular fibres forces the food down the tube, finally lodging 

 it in the first stomach. Tracing the coiu'se of the gullet we find 

 that on leaving the pharynx it passes down the neck, at first be- 

 hind the Avindpipe, then inclines to the left of it, entering the 

 chest cavity in company witli it; it then joasses to the upper side 

 of the trachea over the base of the heart, through the muscle 

 dividing the chest from the abdominal cavity, and which Is 

 called the diaphragm, and entering the stomach by a funnel- 



