40G ANATOMY OF VERTEBRATES. 



the massetcr, forward below tlic zygoma, is called ( socia pa- 

 rotidis ; ' and in some cases it sends its secretion by one or two 

 small tributary canals into the main duct. This crosses the 



*/ 



massetcr, perforates the buccinator, glides between that muscle 

 and the mucous membrane of the mouth, which it finally per- 

 forates opposite the penultimate upper molar, m 2. The parotid 

 derives its arterial supply from the ectocarotid, directly and 

 through the medium of branches ; the disposition of the terminal 

 capillaries resembles that shown in fig. 304. The nerves are 

 derived from the facial, the anterior auricular, and the ex- 

 ternal carotid plexus. The submaxillary gland, much smaller 

 than the parotid and larger than the sublingual, is situated in 

 the anterior portion of the digastric space. It is irregularly ob- 

 long in form, and is enclosed in a loose investment of areolar 



O y 



tissue more delicate than that covering the parotid. Its long 

 axis is directed from before backward, and is about an inch and 

 a half in extent. Its external or maxillary surface is slightly 

 concave, is lodged in a groove in the bone, and is in immediate 

 contact with the mylo-hyoid nerve. The anterior extremity is 

 the smallest, and from the part represented by the confluence of 

 the inner and outer surfaces above, generally proceeds a process, 

 longer than the gland itself, and passing along the upper surface 

 of the mylo-hyoid muscle in company with the excretory duct, 

 but above it, as far as the sublingual gland in front, with which 

 it is occasionally incorporated. This process may be regarded as 

 analogous to the accessory gland of the parotid, and like it varies 

 considerably in size and relation to the body of the gland. A 

 quarter of an inch below the base of the process appears the com- 

 mencement of the excretory duct. It accompanies the gustatory 

 nerve toward the tip of the tongue between the sublingual gland 

 and the genio-hyo-glossus muscle to the side of the fraenum 

 lingua? : in the terminal part of its course it is directed forward 

 and inward, fig. 306, b, lies immediately beneath the mucous 

 membrane, and opens by a very narrow orifice into the mouth, 

 in the centre of a papilla of mucous membrane which projects 

 from the side of the fraenum. The duct is about two inches in 

 length, its coats are more delicate and extensible than those of 

 the parotid. Its calibre exceeds that of the parotid duct, and, 

 like it, its narrowest portion is that immediately beneath the 

 mucous membrane, and this gradually contracts more and more, 

 so that the terminal orifice becomes so small as scarcely to be 

 visible by the naked eye. The primary lobes of the submaxillary 

 gland are much larger than those of the parotid, and the lobules 



