The relations of the external carotid artery, and its terminal branches, the external jugular vein, the facial and the anterior auricular nerve, and the further relative anatomy of the gland, have been already fully entered into.* We may rnention, however, that in the sub stance of the parotid, i. e. in the cellular tis sue between its lobules a little below the surface, are embedded one or more lymphatic glands which can at a glance be recognised from the structure of the parotid by their brown colour, smooth surface, and compara tive density. These glands not unfrequently undergo morbid changes, and by their gradual enlargement cause progressive atrophy of the parotid itself, and ulthnately assume its ana tomical position, This circumstance consti tutes therefore an important element in the inquiry as to the nature of any morbid growth occupying the parotid space, but which it would be out of place here further to allude to.
The Duct of the Parotid Gland, called also the Duct of Steno, emerges from above the middle of its anterior border, accompanied by several branches of the portio dura, runs hori zontally forwards across the masseter muscle as far as its buccal border, passing about half an inch below the zygoma, and immediately below the accessory gland and transverse facial artery. Having reached the anterior border of the masseter, it curves over a mass of fat between it and the buccinator; forming then a very obtuse angle, it perforates the latter, and glides between it and the mucous mem brane of the mouth, which it perforates oppo site the second upper molar tooth.
This terminal oblique portion is about the fifth of an inch in extent, and has justly been compared by Cruveilhier to the vesical portion of the ureter, which, after having perforated the muscular tunic of the bladder, runs for the extent of an inch between it and the mucous membrane.
The parotid duct is from two and a half to three inches in length, and is covered over by a prolongation of the areolar tissue which forms the investment of the body of the gland. This can be distinctly traced as far as the point at which it perforates the buccinator, and here it is surrounded by an aponeurotic expansion derived from the tendon of that muscle, and by a series of glands continuous with the genial glands, the ducts of which open partly into it and partly into the mouth. Having removed the external cellular covering of the duct, its true middle or fibrous coat is observed, giving it a distinct opaque white appearance. It is strong, dense, and elastic. Its thinnest portion is over the oblique part of the duct that glides between the muscular and mucous lining of the buccal cavity, its thickest that covering that part of it between the buccinator and the masseter, the remainder of the duct having this coat developed to an intermediate extent. Beneath the middle coat is the mucous lining, the cylindrical epithelium of which commences, according to Henle, suddenly at the excretory orifice, and con tinues as far as the delicate divisions of the duct in the substance of the gland. The cells
of this epithelium in the main duct range from the to the ra-,- part of an inch in their long diameter.
The parotid derives its arterial supply from the main trunk of the external carotid, the supel ficial temporal, transverse facial, anterior and posterior auricular : its venous, from ves sels of the same name. The lymphatics ter minate in the superficial and deep facial and cervical glands. The nerves are derived froni 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 digas tric space. It is irregularly oblong in form, and is enclosed in a loose investment of areolar tissue more delicate than that cover ing the parotid. Its long axis is directed from before backwards, and is about an inch and a half in extent. Its external or maxil lary surface is slightly concave, is lodged in a groove in the bone, and is in immediate contact with the mylo-hyoid nerve. The inferior or platysmal surface is in relation with the platysma-myoides and superficial cervical fascia, constituting, in fact, that part of the gland which is seen on reflecting that muscle. The internal surface, which looks slightly upwards, is in relation with the pos terior third of the mylo-hyoid muscle, the tendon of the digastric, and the stylo-hyoid and stylo-glossus. The anterior extremity, which is smaller than the posterior, impinges on the anterior belly of the digastric. The posterior border is deeply grooved by the facial artery and vein, which are occasionally sur rounded entirely by the structure of the gland. From the narrow-est portion of the gland, which would be represented by the confluence of the inner and outer surfaces above, gene rally 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 oc casionally incorporated. This process may be regarded as analogous to the accessory gland of the parotid, and like it varies con siderably in size and relation to the body of the gland. In a subject recently examined, we found it represented by two accessory glands, the upper or larger being about the size of a horse-bean, embracing the poste rior half of the lower border of the sublin gual gland, and grooved behind by the trunk of the gustatory nerve. It opened by a dis tinct duct, more than half an inch in length, into the main canal about the middle of its upper border : the other accessory gland, very small, situate half an inch further back, and also communicating with the lower border of the main duct by a canal one-sixth of an inch long. The primary lobes of the submaxillary gland are much larger than those of the paro tid, and the lobules have an irregularly trian gular arrangement.