CH. xxxv.] DEGLUTITION. 5*9 



In vegetable feeders, on the other hand, insalivation is a much 

 more important process. This is especially so in the ruminants ; 

 in these animals, the grass, &c. taken, is hurriedly swallowed, 

 and passes into the first compartment of their four-chambered 

 stomach. Later on, it is returned to the mouth in small instal- 

 ments for thorough mastication and insalivation ; it is then once 

 more swallowed and passes on to the digestive regions of the 

 stomach. This is the act of rumination or " chewing the cud." 



In man, mastication is also an important process, and in people 

 who have lost their teeth severe dyspepsia is often produced, 

 which can be cured by a new set of teeth. 



DEGLUTITION. 



When properly masticated, the food is transmitted in successive 

 portions to the stomach by the act of deglutition or swallowing. 

 This, for the purpose of description, may be divided into three 

 acts. In the first, particles of food collected as a bolus are 

 made to glide between the surface of the tongue and the palatine 

 arch, till they have passed the anterior arch of the fauces ; in the 

 second, the morsel is carried through the pharynx ; and in the 

 third, it reaches the stomach through the oesophagus. These 

 three acts follow each other rapidly. (r.) The first act is 

 voluntary, although it is usually performed unconsciously ; the 

 morsel of food when sufficiently masticated, is pressed between 

 the tongue and palate, by the agency of the muscles of the former, 

 in such a manner as to force it back to the entrance of the 

 pharynx. (2.) The second act is the most complicated, because 

 the food must go past the posterior orifice of the nose and the 

 upper opening of the larynx without entering them. When it 

 has been brought, by the first act, between the anterior arches of 

 the palate, it is moved onwards by the movement of the tongue 

 backwards, and by the muscles of the anterior arches contracting 

 on it and then behind it. The root of the tongue being retracted, 

 and the larynx being raised with the pharynx and carried for- 

 wards under the base of the tongue, the epiglottis is pressed over 

 the upper opening of the larynx, and the morsel glides past it ; 

 the closure of the glottis is additionally secured by the simul- 

 taneous contraction of its own muscles : so that, even when the 

 epiglottis is destroyed, there is little danger of food passing 

 into the larynx so long as its muscles can act freely. In man, 

 and some other animals, the epiglottis is not drawn as a lid 

 over the larynx during swallowing. At the same time, the raising 

 of the soft palate, so that its posterior edge touches the back 

 part of the pharynx, and the approximation of the sides of 



