l6o ANATOMY OF THE SALIVARY GLANDS IN THE CARNIVORA 



that the boundary passes between the orifices of the tliird and fourth 

 orbital glands, while the whole series develop from sprouts in the 

 course of the secondary buccal sulcus. 



The vestibule, thus limited entad, comprises a buccal portion 

 and labial portions, the latter divided into alveobuccal and alveolabial 

 sulci. The angulus oris corresponds to the last cusp of the upper car- 

 nassial. Caudal to this the cheek is formed by the buccinator, which 

 has a sagittal direction, and the masseter, the ental surface of wliich 

 slopes mesad and caudad. The border of the masseter is visible as a 

 slight ridge extending obhquely from the tuberosity of the maxilla to 

 the mandible at the level of the last lower tooth (Figs, i and 2, jo). 

 The superficial facial vein (35) can be seen through the mucosa follow- 

 ing this border, while the deep facial vein (j_/) crosses it obliquely to 

 disappear at the border of the maxilla as it ascends to the orbit. 



The glands of this portion of the vestibule open upon a low stomal 

 ridge (75) which begins opposite the third cusp of the carnassial, crosses 

 the border of the masseter in a sagittal direction, and then turns meso- 

 caudad across the deep facial vein to terminate in the trigonum glandu- 

 lare. From the deep facial vein caudad it is indistinct, and can be easily 

 obhterated by traction. It is separated from the alveolus and border of 

 the hard palate bya shallowsulcus continuous with that between the up- 

 per lip and alveolar process, the equivalents respectively of the secon- 

 dary buccal and superior alveobuccal sulci of the embryo. The orifice of 

 the parotid (j) is at the cranial extremity of the fold opposite the in- 

 terval between the mid and third cusps of the carnassial. The next 

 constant orifice is that of the first orbital (w) opposite the caudal 

 extremity of the carnassial. At an interval of about 2 millimeters 

 follows the orifice of the second orbital (ii). That of the tliird is at the 

 point where the stomal ridge crosses the deep facial vein {12). Caudal 

 to this again in the region of the glandular trigone are several minute 

 orifices set in an irregular row at the end of the ridge and just beyond 

 its termination. A minute osculum {<S) was once seen between the 

 orifice of the parotid and that of the first orbital gland. It was situa- 

 ted on the summit of the ridge and accurately in fine with the other 

 orifices. It corresponds in site with one of the positions of the orbito- 

 parotid of the embryo. In the serial sections of this region in the adult 

 a few minute glands are found scattered along the stomal ridge. Their 



