440 THE DIGESTIVE APPABATUS IN MAMMALIA. 



4. Molar glands.— These are more developed in Kuminants than in Solipeds. The uppei 

 one is enlarged at its posterior extremity. Their nerves come from the buccal nerve. 



Pig.— The parotid gland of this animal is little developed, as in Ruminants, and Steiio's 

 duct fullows the posterior border of tlie lower jaw. (Leyh says that it is, proportionately, 

 largely developed ; that its upper end does not reach the concha of the ear, and that Steno's 

 duct opens at the sixth molar.) 



The sublingual gland is analogous in its disposition to that of the Ox. Cuvier, in his 

 Lecons d'A7iatomie Compar^e, indicates this :— " The Pig has two sublingual glands. One, 

 very long and narrow, accompanies, outwardly, the excretory canal of the submaxillary gland, 

 from the angle of the jaw to tiie second sublingual. It is composed of small lobules of a pale 

 red colour. Its excretory duct arises near the posterior third, and passes along with, but to 

 the outside of, the submaxillary duct. It terminates near the orifice of the latter by a small 

 opening; its diameter is equally small. The second sublingual gland is placid before the 

 first ; its' form is square and flattened, and the lobes of which it is composed are larger and 

 redder. It has from eight to ten excretory ducts." (In this animal the duct of Wharton does 

 not open into the mouth by a papilla ; consequently, there is no barb.) 



Camivora.— The parotid of the Dog and Cat is small, and Steno's duct always passes 

 through the masseter. (It opens at the fourth molar in the Dog, and the third in the Cat.) 



In the Dog, the mhmaxillary glands are larger than the parotids. " They even have in 

 front, along Wharton's duct, a small accessory gland, with a distinct excretory caiial opening 

 into the tame papilla as Wharton's." (Leyh states that the submaxillary duct does not project 

 into the mouth.) The supplementary gland is absent in the Cat. 



The sublingual gland is not present in the Dog ; it is very .'<mall in the Cat, and carried 

 further back than in the other animals. (Leyh describes a sublingual gland as jiresent in tht 

 Camivora, which is divided into two portions, as in the Pig : the anterior being formed of 

 detached lobules that open into the mouth by several ducts ; and the posterior, larger above 

 than below, with two ducts, the s;i;aller opening into Wharton's duct, and the larger a little in 

 front of it.) 



The upper molar gland of the Dog, scarcely noticeable for the greater part of its extent, 

 forms posteriorly, under the zygomatic arch, near the eye, an independent lobe, remarkable for 

 its large size and its single excretory duct. Duvernoy, who first described it, proposed to name 

 it the suhzygomatic gland. It is not present in the Cat. (This is doubtless the organ 

 described by Leyh as the orbital gland, which, he says, is only found in the Dog ; the superior 

 molar gland, according to him, not existing in that animal. This orbital gland is external to 

 the ocular muscles, has three or four excretory canals— the ductus Nuckiani — which converge 

 into one duct that opens into the month above the last molar.) 



The labial, lingual, and staplnjUne glandulx are much less developed in the Camivora than 

 the Herbivora. This predominance of the salivary system in the latter is sufficiently 

 accounted for, when we consider the hard, fibrous, and coriaceous food these animals live upon, 

 and which must be ingested in large quantity, because of the small amount of nutrition 

 it contains. For its mastication and deglutition, a great amount of saliva is absolutely 

 necessary. 



Bodents. — In the Rabbit, the inferior molar gland is very large. In addition to the 

 salivary glands already described, this animal has a small gland outside the buccinator muscle, 

 along the interior maxilla, at the mental foramen. 



Comparison of the Salivary Glands of Man with those op Animals. 



As in animals, the parotid is the most voluminous of the salivary glands. Its tissue is 

 reddish-grey and lobulated, the lobules adhering closely to each other. Its shape is irregular, 

 and it is moulded to the excavation behind the angle of the jaw. Steno's duct passes across 

 the masseter, and shows on its eourse some salivary lobules, forming what is named the 

 accessory parotid (or socia parotidis) ; it opens opposite the third upper molar. 



The submaxillary gland weighs about half an ounce. It is partly situated beneath the 

 deep cervical fascia, and partly within the body of the lower jaw, between the mylo-hyoideus 

 and hyo-glossus muscles. Its lobules are more loosely united than those of the parotid. 

 Wharton's duct opens on the sides of the frjenum linguae by a small opening at the apex of a 

 round papilla (caruncida sublingualis). 



The sublingual gland is analogous to that of the Ox and Pig. There are, in fact, two 

 sublinguals : an anterior about the size of an almond, and furnished with a single excretory 

 canal— the ductus Bartholini, that terminates near Wharton's duct; the other, posterior, 

 formed by several isolated lobules with multiple excretory ducts — the ductus Riviniani. 



