238 



HAND-BOOK OF PHYSIOLOGY. 



DEGLUTITION OR SWALLOWING. 



When properly masticated, the food is transmitted in successive por- 

 tions 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 to a morsel are made to glide between the sur- 

 face 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 



FIG. 174. 



FIG. 175. 



FIG. 174. Section of a mucous gland from the tongue. A, opening of the duct on the free sur- 

 face; C, basement membrane with nuclei; B, flattened epithelial cells lining duct. The duct divides 

 into several branches, which are convoluted and end blindly, being lined throughout by columnar 

 epithelium. D, lumen of one of the tubuli of the gland, x !X). (Klein and Noble Smith.) 



FIG. 175. Longitudinal section of oesophagus of a dog toward the lower end. a, stratified epithe- 

 lium of the mucous membrane; 6, mucous membrane proper; c, duct of mucous gland; d, muscu- 

 laris mucosae ; e, mucous glands;/, submucous coat; g, circular muscular layer; /i, intermuscular 

 layer, in which is contained the ganglion cells of Auerbach; i, longitudinal muscular layer; A-, outside 

 investment of fibrous tissue. X 100. (V. D. Harris.) 



pharynx; and in the third, it reaches the stomach through the oesophagus. 

 These three acts follow each other rapidly. (1.) Tli3 first act of deglutition 

 may be voluntary, although it is usually performed unconsciously; the 

 morsel of food, when sufficiently masticated, being 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 pass by the 



