DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 23 1 



deflected flange, a continuation of that of the parotid (Figs. 63, 64) ; 

 in the last section it appears to be forming a sprout. In this region 

 the anlage of the masseter, which is as yet hardly distinct from that of 

 the zygoma, comes closer than elsewhere to the buccal sulcus, and is 

 now absolutely nearer than in embryo No. 189 (Figs 55-57), the 

 deep facial vein and a small quantity of mesenchyme intervening. 

 The appearances in Fig. 62 require comment. This is the first section 

 in which the parotid is free. It will be seen that the mesenchyme in 

 the interval between the sprout and the buccal sulcus is more dense 

 than in the succeeding sections (F'gs. 63, 64), and that where the epi- 

 thelium of the mouth and of the anlage impinge upon this area, their 

 outlines become indefinite. This may be due to their being covered 

 in the thick section by the mesenchyme at these points. On the 

 other hand, it is likely that epithehum is here being destroyed; the 

 intermediate portion of the flange actually does disappear subse- 

 quently, and quite regularly at its caudal border appears a similar 

 thickening of the mesenchyme and obscuration of the ectal outline 

 of the epithelium. In other cases where epithelial structures are 

 undergoing reduction like conditions are seen, as, for example, in the 

 orbitoparotid flange in Fig. 65. 



From this period the sprout grows actively into the mesenchyme 

 and the anlage comes to extend through considerable series of sections. 

 It will be convenient to follow the changes in the flange first in detail, 

 and deal subsequently with distal conditions in a more summary 

 manner. With regard to the attachment of the anlage we have to 

 consider, first, the transformation of the flangelike attachment into 

 the circular orifice of the adult and, second, the mode in which the 

 position of the attachment is shifted away from the buccal sulcus. 

 For the satisfactory analysis of this latter process it will be necessary 

 to enter somewhat upon the changes in the vestibule, by which it is 

 transformed from a horizontal to a vertical space. 



In the 15 milHmeter embryo, No. 219, the parotid anlage is a solid 

 retort-shaped object, attached to the buccal sulcus in a fundal position, 

 a little caudal of the midpoint between the angulus oris and the bucco- 

 masseteric nerve (Fig. 44). The latter, which is not represented 

 in the cut, occupies the angle between the pars cylindrica (8) and the 

 lateral process (9) of the orbital inclusion. The parotid flange and 



