228 DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



meter embryo, but as it projects ventrad it is not seen in the view 

 of the model here shown. 



Conditions in an embryo of 13.5 millimeters are shown in Fig. 35 

 from a model of the ectal surface of the entire oral epithelium ; in 

 Fig. 34 the left buccal sulcus and its anlages are represented on a 

 larger scale. The buccal sulcus has a distinct sagittal arch, the crown 

 of which the pars lata (7) of the orbital inclusion now occupies. The 

 flexures, the postangular bend, and the orbital angle are well defined ; 

 about midway between them is the triangular flange of the parotid 

 (12). A section of the head passing through this anlage is shown in 

 Fig. 36, which gives an indication of the relative size and topography 

 of the structure in a stage which it is necessary to study in some detail. 

 On the right the triangular anlage of the zygoma is seen a short dis- 

 tance dorsal to the parotid, while the facial vein is shown as a comma- 

 shaped dark object lying lateral and ventral to the anlage. On the 

 left the small subparotid mesenchyme condensation shows clearly. 

 A complete series of sections of the anlage of the right side is given on 

 a larger scale in Figs. 49-57. The flange, which is sulcal in attachment, 

 extends through six sections (80 fi) ; in five it increases in width 

 (Figs. 50-54). In the next section it is narrow and its outlines are 

 obscured by a greater density of the mesenchyme (Fig. 55), a usual 

 feature of the caudal section of the flange. In Figs. 56 and 57 we enter 

 upon the orbitoparotid interval, where, apart from the angularity 

 of the buccal sulcus, there is no evidence of compression. Here 

 the anlages of the zygoma and as yet scarcely differentiated masseter 

 are somewhat nearer the sukus than in the more cranial sections. 

 The lateral border is thickened in its section of greatest breadth 

 (Fig. 54) and in the one preceding it (Fig. 53). In these sections the 

 intermediate portion of the flange, between the thickened border and 

 the buccal sulcus, appears compressed, and here, also, the subparotid 

 area in the mesenchyme is most clearly defined. Turning now to 

 the conditions obtaining in the epithelium of the flange itself and in the 

 adjacent portion of the oral cavity, a periderm layer is seen to be 

 everywhere present. This is composed of a single layer of domed 

 ceOs except at the buccal sulcus, where it accumulates and partially 

 fills the fundus (Fig. 49). In this section a small tearlike fissure 

 invades the mass of periderm. In Fig. 50 the fissure is larger and 



