ANATOMY. 



unly reduce the food into a powder, or at 

 all events into a dry mass, that could not 

 be swallowed without great difficulty. To 

 obviate this inconvenience, it is plentiful- 

 ly moistened with a watery fluid called 

 saliva, and is thereby converted into a soft 

 paste, which can be conveyed into the 

 stomach with perfect facility. The source 

 of this fluid is, in several glandular bodies, 

 situated near the mouth, and se lading ex- 

 cretory ducts, which convey the secret- 

 ed fluid into that cavity. As the jaws 

 move, the muscles compress these glands, 

 and squeeze the secreted fluid into the 

 moutU. The tongue is constantly em- 

 ployed in bringing again under the action 

 of the teeth those portions of the food 

 which escape from between them; and 

 the closure of the lips prevents it from 

 fulling out of the mouth. 



The true salivary glands are three in 

 number, on each side of the head. The 

 largest is placed in the space left between 

 the ear and the lower-jaw-bone ; and is 

 called, from its situation, the parotid. Its 

 duct pierces the middle of the cheek. 

 The two others are placed under the 

 tongue, and are called the submaxillary 

 and sublingual. Their ducts join, to open 

 by a common orifice, at the side of the 

 membrane called the frenum of the 

 tongue, which ties the under surface of 

 that organ to the inside of the lower jaw. 

 Besides these large salivary glands, there 

 are other small granular bodies, which 

 pour a mucous fluid into the mouth ; 

 these are named, according to their situa- 

 tion, glandulae labiales, buccales, &c. 



The cavity of the mouth in which the 

 process of mastication goes on is not a 

 very extensive one. There is a small 

 space left between the cheeks and the 

 teeth externally; but within the teeth the 

 tongue occupies nearly the whole room. 

 The upper boundary is formed by the pa- 

 late or roof of the mouth, and the lower 

 by the surface of the tongue. The mouth 

 opens behind, by a tolerablefree commu- 

 nication, into a membranous bag, called 

 the pharynx. The surface of the mouth 

 is every where covered by a soft and 

 smooth membrane. This is of course 

 kept constantly in a moist state, as the 

 glandsabove enumeratedcontinually pour 

 more or less of their secretion into the 

 cavity. The membrane of the mouth is 

 continuous with the external surface of 

 the body ; but the skin assumes a more 

 delicate organization, as must be appa- 

 rent to every body, from the change of 

 colour at the lips. 



Bar of the pharynx. -The masticated 



aliment is collected on the back of th 

 tongue, which is then carried upwards, 

 and backwards, to discharge it into the 

 pharynx. This bag is covered by t;uscu- 

 lar fibres (forming the muscles called 

 constrictores pharyngis) which contract, 

 successively, in order to propel the food 

 towards the stomach. But as there are 

 several organs communicating with the 

 pharynx, the food might pass in a Wrong 

 direction, if the parts were not so con- 

 trived as to prevent such occurrences. 



In the upper and anterior part of the 

 pharynx, the nostrils open by two large 

 and free apertures. Between these and 

 the entrance from the mouth is found a 

 fleshy and moveable curtain, called the 

 soft palate, or velum pendulum palati. 

 There is a small body of a pointed figure, 

 projecting from the middle of this organ, 

 and known by the name of the uvula. 

 This curtain and the uvula can be easily 

 seen in the throat of a living person. It 

 admits of being elevated so as to shut 

 the opening of the nostrils; and its ac- 

 tion is exemplified in the act of vomiting: 

 the food is forcibly thrown into the pha- 

 rynx, and would pass mostly into the 

 nose, were it not prevented by the soft 

 palate. From the uvula the membrane is 

 continued on either side, in an arched 

 form, towards the root of the tongue, and 

 it contains a glandular body, called the 

 tonsil, which secretes a mucous fluid, to 

 lubricate the parts, and facilitate the pas- 

 sage of the aliment. The larynx opens 

 into the pharynx, just at the root of the 

 tongue ; over this part, which is termed 

 the glottis, every morsel of the food must 

 necessarily pass : yet so exquisitely ten- 

 der is the membrane of the wind-pipe, 

 that the contact of the smallest extrane- 

 ous body excites a convulsive paroxysm 

 of coughing, that does not cease until the 

 offending matter be removed. Here then 

 are two objects to be effected ; the func- 

 tion of respiration requires that the wind- 

 pipe should have a free cummunication 

 with the external air, while the irritable 

 nature of its membrane demands that no 

 extraneous body should find admission. 

 These points are both attained by means 

 of a strictly mechanical contrivance ; by 

 a structure which produces the required 

 effect independently of the will of the 

 animal, and merely in -consequence of 

 those motions which the organs perform 

 in the office of deg-lutition. At the back 

 of the tongue, and just in front of the 

 glottis, is a cartilaginous valve, called the 

 epiglottis. When the parts are at rest, 

 this valve stands perpendicular, and con- 



