174 



MOUTH DIGESTION. 



long and opens at the side of the frenum of the tongue. Its 

 nerves come from the submaxillary ganglion, and consist of fila- 

 ments of the chorda tympani of the facial and lingual branch of 

 the inferior maxillary, of the mylohyoid branch of the inferior 

 dental, and of the sympathetic. 



The sublingual gland lies under the mucous membrane, at the 

 side of the frenum of the tongue. Its secretion is discharged 

 through from eight to twenty ducts, ducts of Rivinus, which open 

 on the prominence of the mucous membrane made by the gland 

 beneath. Sometimes two or more of these ducts join, and form 

 the duct of Bartholin, which opens into Wharton's duct. The 

 nerves of this gland are branches of the lingual. 



Besides these three sets of glands there are numerous mucous 

 glands on the dorsum and the edges of the tongue, in the tonsil, 

 and the soft palate, whose secretion is a constituent of the saliva. 

 The salivary glands belong to the class ordinarily described as 

 compound racemose glands. Inasmuch, however, as the secreting 

 portions are not sacs, which are characteristic of racemose glands, 

 but tubes, this variety of gland is perhaps better denominated 

 compound tubular. It consists of lobes, which in turn are made 

 up of lobules, each of which is composed of tubular alveoli or 

 acini connected with a duct. The ducts from different lobules 

 join together to form larger ducts, and finally all combine to form 

 the main duct of the gland. 



Mucous (Fig. 97) and Albuminous Glands. Two types of 



glands are recognized 

 by histologists accord- 

 ing to the product and 

 the appearance of the 

 cells within the alveoli 

 of the salivary glands : 

 mucous and albuminous 

 or serous. 



The mucous gland 

 secretes a tenacious fluid 

 containing mucin, and 

 the cells are relatively 

 large and clear, and 

 have been described as 

 resembling ground 

 glass ; their granules 

 are ordinarily indistinct. 

 The sublingual and the mucous 'glands of the mouth are repre- 

 sentatives of this type. 



These glands also contain demilunes of Heidenhain or crescentic 

 cells, which are placed between the mucous cells and the base- 

 ment-membrane (Fig. 97). Heidenhain, whose name they bear, 



FIG. 97. Mucous gland : submaxillary of dog 

 resting stage. 



