30 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



extent of the buccal sulcus. The sulcus increases in length, apparently 

 by the addition of successive increments from in front, as the maxillary 

 and mandibular processes increase in size and their area of coalescence 

 enlarges. In this new segment the fold of origin of the parotid appears 

 close to the angulus oris. It therefore appears that the buccal sulcus 

 is subject to two distinct processes of folding ; one advances caudo- 

 craniad (the orbital fold), while the other, later in time and of less 

 extent, affects the cranial segment of the sulcus (parotid fold). There 

 regularly intervenes between the folds a segment of the sulcus which 

 escapes compression, the orhito parotid interval. This, like the rest 

 of the furrow, is lined with thickened epithelium. It is subject to a 

 wide range of variation, in length, in becoming encroached upon 

 secondarily by the orbital fold, and in the development of independent 

 sprouts from its epithelium. Rarely the whole segment becomes 

 involved in the process of folding and a flange is formed connecting the 

 cranial extremity of the orbital inclusion with the parotid, the orhito- 

 parotid bridge. A constriction and separation of this in toto from the 

 oral epithelium has not been observ^ed in the cat. Always the process 

 is interrupted ; the interruption, however, varies considerably in site 

 and extent. Any portion of the flange may give rise to a sprout ; 

 this variant is common. The sprout may arise from the cranial 

 extremity of the flange in continuity with the parotid anlage ; in its 

 later stages this condition presents itself as a small branch arising at 

 the junction of the parotid duct with the oral epithelium. Less 

 frequently a branch is attached to the parotid duct, between its orifice 

 and the cranial border of the masseter. If, however, the sprout 

 takes origin from an intermediate portion of the bridge, it will in its 

 later stages appear as a plug arising directly from the oral epithelium, 

 the direction of which may be parallel to the parotid duct or parallel 

 to the buccal sulcus. These elements are termed orhito parotids. 

 Occasionally they become entirely separated from the mouth and 

 form orbito parotid inclusions. 



The buccal sulcus in the first phase of its activity in the cat is 

 thus seen to produce from a common epithelial anlage two constant 

 elements, the parotid and the orbital inclusion, separated by a variable 

 orbitoparotid interval, over which the anlages may be continuous by 

 a flange, the orbitoparotid bridge. The interval is capable of gi\'ing 



