DIGESTIVE SYSTEM. 239 



of the arterial trunks is filled with injection, it rarely happens that 

 the opposite half of the organ receives any colouring from it. Its 

 nerves are the ninth pair, which run to the muscles, and a con- 

 siderable branch from the fifth pair, in whose extreme ramifica- 

 tions, which are distributed to the papillae, the perception of taste 

 is supposed to be inherent. 



OF THE SALIVARY GLANDS. 



Number and Names. — The salivary glands, properly so called, 

 are six in number, three upon each side of the head ; — the parotid, 

 the submaxillary, and the sublingual. 



THE PAROTID, the largest of these glands, so called from 

 being placed near the ear, lies within a hollow space at the upper 

 and back part of the head, bounded by the branch of the lower 

 jaw before, and the petrous portion of the temporal bone behind: 

 it extends as high up as the root of the ear, and as low down as 

 the angle of the jaw, by which latter a small portion of it is con- 

 cealed. This gland, like the others of the same class, is enveloped 

 in a case of dense cellular membrane, and is constituted, in struc- 

 ture, of many little lobes or lobuli, connected together by pro- 

 cesses transmitted into the interior from this cellular covering. 

 Every lobulus is composed of a distinct set of secretory vessels, 

 from which numerous tubitli arise, conjoin, and at length form 

 one main branch ; these branches, which correspond in number 

 to the lobuli, unite and re-unite until they end in one common 

 excretory duct. The duct emerges from the inferior part of the 

 gland, runs along the inner part of the angle of the jaw, and 

 crosses over the posterior edge of the bone immediately above or 

 behind the submaxillary artery and vein : in the remainder of its 

 course it corresponds to the border of the masseter, and, about 

 opposite to the second anterior molar tooth, pierces obliquely the 

 buccinator, and terminates by a tubercular eminence upon the 

 internal surface of the buccal membrane*. 



THE SUBMAXILLARY GLAND, of smaller volume than 

 the parotid, lies in the space between the angles of the jaw, to 

 which, and to the muscles thereabouts, it is loosely attached by 

 cellular membrane: a portion of it is also generally found pro- 



* To expose this duct, at or near its issue from the gland, an incision 

 should be carried along the posterior border of the branch of the lower 

 jaw : iirst, dividing the skin ; secondly, the panniculus ; thirdly, the cellular 

 tissue immediately covering the duct, which is readily distinguished by its 

 glistening pellucid aspect. By extending the incision around the angle of 

 the jaw, directing it towards the inner edge of the bone, the duct will be 

 found making its first turn : here, however, it is lodged in a huUow, deeply 

 buried in cellular tissue. 



