The salivary glands, according to the re searches of Huschke, are more voluminous, in proportion to the bulk of the body, in the infant than the adult, the submaxillary and sublingual, however, being proportionately larger than the parotid. In the adult, on the other hand, the parotid is, in proportion to the bulk of the body, larger than the other two.
The subsidiary salivary The labial, buccal, molar, palatine, posterior, and interior lingual glands may without any impropriety be reckoned among the glands of the salivary apparatus, being identical in their structure, and provided with excretory ducts opening on to the free surface of the mucous mem brane. Varying materially in size, and irre gularly rounded or flattened, they exude a slightly viscid saliva by their orifices, which are visible to the unassisted eye.
We have already stated that the posterior part of the sublingual gland is occasionally represented by one or more distinct glands in juxta-position, each furnished with a very short excretory duct. These distinct lobes of the gland are in every way analo,gous to one of the molar glands or larger labial. It will thus be observed that the transition of the primary to the subsidiary glands is by no means rapid, but that they run the one into the other by insensible gradations, the sub lingual gland passing from the one series into the other. A molar, labial, or buccal gland, with its excretory duct, might then be not inaptly compared, according to its size, to a secondary or tertiary lobule of the parotid, or submaxillary.
The labial glands form a series of closely packed small spheroidal glands, of consider able density,,situated in the areolar tissue between the mucous membrane of the mouth and the orbicularis oris muscle, and in relation above and below, consequently, with the upper and lower lip. They are not of uniform volume or number. Sebastian* has observed as many as fifty-seven in the lower lip, and in other instances from thirteen to twenty one, their size increasing in the inverse ratio to their number. They are more nu merous in the infant than in the adult. Their excretory ducts open perpendicularly or ob liquely into the vestibule of the mouth on the posterior or free surface of the labial mucous membrane. They are not visible–to the eye
when the lips are in their natural lax position, but when the latter are everted, so that the mucous membrane is rendered tense, they form considerable projections.
The buccal glands are exactly analogous to the labial glands in form and position, being irregularly spheroidal, and placed between the buccinator and mucous membrane, and open by the orifices of distinct ducts on to the free surface of the latter. They are, however, smaller.
The molar glands—two, three, or four in number—form an exception as regards their situation to the above glands, being placed between the buccinator and masseter muscles. They are also larger and more dense, being composed of several lobes. The ducts ter minate by opening on to the mucous mem brane at the posterior part of the cheek. In a subject we recently examined, their ter minal orifices were arran.ed horizontally at unequal distances from eat% other, on a level with the orifice of Steno's duct, but more than half an inch behind it. They were five in number. We have not succeeded in observ ing the communications which the ducts of one or more of these glands is stated by some anatomists to establish with the duct of the parotid.
The palatine glands are very numerous and small, and situated partly between the mucous membrane and the palatine arch, and partly between the MUCOUS and muscular layers of the soft palate. The former are situated on either side of the median line, and form a thick layer, being more closely aggregated together in the front and behind than in the middle, opening on to the mucous membrane by distinct orifices. The latter, smaller than the former, exist both on the upper and lower surface of the veluna, and are continuous below, where they are more numerous than above, with the glands of the hard palate.
The posterior lingual glands are placed at the back part of the tongue, directly behind the large papillx, which form a distinct pro minence at this part. They are spheroidal, and have remarkably short excretory ducts, the circular orifices of vvhich, however, are distinctly visible.