1140 THE DIGESTIVE SYSTEM. 



major (O.T. duct of Bartholin), is very rare, and must be considered as an exceptional condition 

 in man, although normal in the ox, sheep, and goat. The same may also be said of ducts from 

 the sublingual, which are described as opening into the submaxillary duct. 



Vessels and Nerves. The arteries are derived from the sublingual artery, a branch of 

 the lingual, and from the submental, a branch of the external maxillary. The nerves come from 

 the lingual, chorda tympani, and the external maxillary plexus, through a branch of the 

 submaxillary ganglion which joins the lingual, and is conveyed by it to the gland. The 

 secretory fibres run in the chorda tympani nerve, and thence through the submaxillary 

 ganglion to the gland. 



The glandula lingualis anterior (Blandini, Nuhni) has been described with the 

 tongue. 



Structure of the Salivary Glands (Fig. 900). Each of the principal salivary glands consists 

 of a number of lobules, loosely united together by connective tissue. From each of them 

 one or more ducts emerge. Each duct when traced onwards divides into branches, which 

 terminate in a group of saccular or tubular alveoli. 



The epithelium lining the ducts is columnar in character, but becomes flattened at the 

 junction with the alveoli. 



The epithelium lining the alveoli shows different characters in different glands. In the 

 parotid, and the small salivary glands of the vallate papillae in which the secretion is 

 watery or albuminous, the cells are uniform in character, and of small size. When the gland is 

 at rest, the cells are filled with small granules, which when the secretion is poured out are trans- 

 formed into the gland ferment (ptyalin). After secretion, only the deeper parts of the cells show 

 the presence of granules. The nuclei are rounded, and lie near the centre of the cells. In the 

 sublingual, labial, buccal, and other glands of the mouth and palate the secretion is of a mucous 

 character and the cells are larger, and the nuclei are placed deeply. The cells appear clear and 

 swollen unless special methods of preparation are employed. In such cases, e.g., when examined 

 in serum, the cells are seen to contain large and distinct granules of mucigen which in secretion | 

 are transformed into mucus. 



In the submaxillary gland and the anterior lingual gland both varieties of cells are 

 present. In these cases, the larger, clear mucous cells line the cavity of the alveolus, and the] 

 smaller granular serous cells are arranged upon the basement membrane, deep to the former, 

 cells, in crescentic masses, termed the crescents or demilunes of Gianuzzi. They communicate with j 

 the cavity of the alveolus by small channels between adjacent mucous cells. 



After secretion, the mucous cells become smaller, and stain more deeply than when loaded 

 with mucigen before secretion. 



PHAKYNX. 



The pharynx is the expanded upper portion of the alimentary canal which lies 

 posterior to and communicates with the mouth, the larynx, and the nasaLcavities, and' 

 is continuous inferiorly with the superior end of the oesophagus or gullet (Fig. 901) 



It extends from the base of the skull, above, to the level of the sixth cervica" 

 vertebra (Fig. 903) and the lower border of the cricoid cartilage, below. 



Its total length varies from 5 to 5J inches (12*5 to 14*0 cm.). 



The inferior portion alone, that is, the parts lying opposite and inferior to the 

 opening of the mouth, is functionally a part of the alimentary canal, for tht 

 portion above the level of the soft palate is used for respiration only. It is 

 however, convenient to study the structure and relations of the whole of th( 

 pharynx at once. 



Structurally the pharynx is a nbro-muscular bag, of conical form, wide abov< 

 and narrow below. The wall of the superior part of the pharynx, in the regioi 

 of the base of the skull, is firmly attached to the surrounding bony structures 

 especially around the orifice of the choanse, and hence in this superior portion o ' 

 the pharynx there is a permanent cavity containing air. 



The lower portion gradually assumes a more tubular form, and the anterio 

 and posterior walls approach one another, so that below the level of the openin* 

 of the larynx they are in contact with one another, and the cavity is reduced to ; 

 slit, except during the passage of food. 



Dimensions of the Pharynx. From the fornix pharyngis, i.e. the highest part of the roo: 

 to the superior surface of the soft palate at its junction with the hard palate, measures abou 

 1^ inches, or 3 cm. The vertical extent of the oral part of the pharynx is about 2^ inches 

 or 6 cm., and that of the laryngeal part is about 2| inches, or 7 cm. 



The inferior end of the pharynx is usually about 5| to 6^ inches from the margins of t 

 incisor tooth, in a line passing through the cavities of tne mouth and of the oral and laryngec 

 parts of the pharynx. 



The other diameters are as follows: the antero- posterior diameter (depth) of the superic 



