300 DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



Of all these only the inferior alveobuccals are present in the embryos 

 of our series less than 70 miUimeters in length. 



The inferior alveobuccal glands are present in the course of the sulcus 

 of the same name in some of the embryos of 1 7 miUimeters ; in those 

 of 18 millimeters they are constant. The sulcus at this time is a 

 broad, shallow convexity between the buccal sulcus and the inferior 

 dental anlage. It attains its maximimi near the angulus oris and 

 thence diminishes in both directions. The region in a 19 millimeter 

 embryo is shown in Fig. 144. The glands in their inception are small 

 hemispheric elevations composed of basal cells. They are at first 

 few in number and arranged in a single slightly irregular row. A 

 second row is soon added ; this may be present in embryos of 

 18-18. 5 millimeters or still lacking in embryos of 19 millimeters 

 (Fig. 144). The sprouts are at first attached close together in the 

 deepest part of the concavity of the sulcus. In the 25 millimeter 

 embryo (Fig. 158) they have begun to elongate, and form small solid 

 cylinders with very shghtly enlarged rounded extremities. The sprouts 

 are directed ventrolaterad. In the embryos above 31 milUmeters 

 they usually fork at a httle distance from the mouth, though some 

 always lack this division. In the 28 millimeter embryo secondary 

 branches are present. In the 35 millimeter embryo there is a pale 

 axial Une in the duct; a lumen is present in the 51 millimeter embryo. 

 Here the stratum corneum is thick, and a narrow channel without 

 proper wall continues the lumen through it to the surface. The cells 

 adjacent to this passage contain a small quantity of pigment. In the 

 70 millimeter embryo a few of these passages were present in the epi- 

 theUum only, terminating in the layer of basal cells, or in very small 

 cellular projections from its ectal surface. These had not the regular 

 hemispheric contour of early sprouts ; their appearance suggested 

 degeneration. 



While these glands are evidently formed by a simple process of 

 sprouting, their orifices become gradually transferred to the lateral 

 wall of the sulcus. In the 25 millimeter embryo the concavity is 

 somewhat deeper (Fig. 158). In the embryo of 50 millimeters the 

 sulcus is angulate at its fundus (Fig. 159) ; in that of 70 miUimeters 

 it is a deep V-shaped cleft (Fig. 160). In the same embryos the 

 attachment of the glands are seen to be shifted dorsad on the lateral 



