440 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



4 Molar qlnnds -These are more developed in Ruminants than m Solipeds. The uppet 

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



Pis -The parotid gland of this animal is little developed, as in Ruminants, and Stenos 

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

 largely developed; that it. upper end does nut reach the concha of tlie ear, and that fetenoB 

 duct opens at the sixth molar.) , , ^ ., r^ n • ■ v.- 



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

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

 verv long and nar.ow, accompanies, outwardly, the excretory canal of the sabinaxillary gland, 

 from the an-le of the jaw to the 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 

 onenin-- its dian.eter is equallv small. The second sublingual gland is placed before the 

 first- its' form is square a-.d 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 int ■ the n.outh by a papilla ; consequently, there is no barb) 



Carnivora.— The parotid of the Dog and Cat is small, and Stenos duct always passes 

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



In^the Dog the submaxillary glands are larger than the parotids. " They even have in 

 front alonc' Wh'artou's duct, a small accessory gland, with a distinct excretory canal opening 

 into the same 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 small in the Cat, and carried 

 further back than in the other animals. (Leyh describes a sublingual gland as present in thi 

 Carnivora, which is divided into two portions, as in the Pig : the anterior being formed o( 

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

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



front of it.) 



The XLpper 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 lar<^e size and its single excretory duct. Duvernoy, who first described it, jiroposed to name 

 it ihe subziigvmatic gland. It is not present in the Cat. (This is d.-ubtless 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 -t'ne ductus Nuckiani—v/hich converge 

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



The labial, lingual, and staphyline glandulx are much less developi d in the Carnivora 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. 



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

 salivarv "-lands already described, this animal has a small gland outside the buccinator muscle, 

 along the inferior maxilla, at the mental foramen. 



Comparison of the Salivary Glands of Man with those of 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 course 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-globsus muscles. Its lobules are more locisely united than those of the parotid. 

 Wharton's duct opens on the sides of the fisenum linguse by a small opening at the apex of a 

 round papilla (caruncula sublingual is). 



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

 sublinguals: an anterior about the size of an almond, and furnished witii 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. 



