2 74 DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



cranial members of which are accelerated in development and of pre- 

 ponderating size in the adult. They are the product of the second 

 phase of acti\'ity of the caudal portion of the marginal cavity after it 

 has thrown off the orbital inclusion, which has been seen to represent 

 its primitive fundus. A point of interpretation arises here. As has 

 been seen, the secondary buccal sulcus is continuous craniad in the older 

 embryos of this series with the superior alveobuccal sulcus. This 

 sulcus is of late formation, and produced by a simple process of folding 

 between the dental ridge and the buccal sulcus, which is ventrally dis- 

 placed and finally obliterated as the vertical cheek is formed. Behind 

 the border of the masseter its representative is the orbital inclusion. 

 Now from the continuity of the secondary buccal sulcus with the 

 superior alveobuccal, it would seem that the orbital inclusion is the 

 equivalent of the maxillomandibular plane lateral to the alveobuccal 

 sulcus, and that being lost, the secondary buccal sulcus is really the 

 equivalent of the alveobuccal with which it is continuous. If this 

 interpretation is vahd, the orbital glands are homodynamous with the 

 glands of the superior alveobuccal sulcus, that is, superior "molar or 

 buccal" glands, as these terms are commonly used (Fig. 165). 



The elements appear in the course of the secondary buccal sulcus 

 in its postdental segment ; three acquire more cranial orifices, their 

 ducts being carried forward by keels of proliferated epithelium, as is 

 usual with the large salivary glands. The orbitals afford an interest- 

 ing series of the degree of this process, which diminishes from the first 

 orbital to the third, and is apparently lacking in the more caudal 

 elements. It further estabhshes beyond doubt that such advances may 

 be made without relation to a sulcus, and therefore are sometimes, 

 and with a high degree of probabiHty always, the results of a prolif- 

 eration, and not the separation of the border of a flange as such, even 

 when the proliferation advances along this border. 



THE GLANDS OF THE ALVEOLINGUAL REGION 



Here are developed the submaxillary, the greater subhngual, and 

 a few representatives of the lesser sublingual series of glands. The 

 submaxillary is formed in the course of the lingual sulcus, which serves 

 alsb as a line for the advance of its keel. The greater sublingual arises 



