DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 22? 



teric segment, the derivatives of which are in relation with the ental 

 surface of the muscle. Between these two segments, the orbito- 

 parotid interval forms a region of transition and its derivatives show 

 a tendency now to ecto-, now to ento-masseteric, growth. 



In the embryo of 12.5 miUimeters the whole buccal sulcus has length- 

 ened, but especially the preorbital portion. The mesenchyme conden- 

 sation and the accompanying convexity of the floor of the sulcus no 

 longer extend to the angulus oris, though still near it. As the sections 

 are followed caudad, the convexity increases ; the lumen is obUterated at 

 first laterad, then throughout the width of the convexity. The flange 

 slowly attains a ma.ximum breadth to dwindle more rapidly caudad; 

 it increases in width for 65 m, diminishing for 27 /^. It is, then, m the 

 way of assuming a triangular shape. Its absolute width has mcreased ; 

 the enlargement of the free border is more marked and extends from 

 the section of maximum breadth craniad for 40 ^. The proliferation 

 results first in broadening the flange and in modeling a portion of the 

 duct along the oblique edge of the flange, wliile the invasion of the 

 mesenchyme by the free growth of a bud follows later. The anlage is 

 soUd. The orbitoparotid interval has a length of 80 ^ ; here the 

 epithelium of the sulcus is thick, but there is no sign of folding. The 

 anlage of the masscter appears immediately lateral to it in the sections. 

 The anterior process of the orbital inclusion is well defined ; its sec- 

 tions show it to be a flange with an axial periderm Une opening mesad 



into a fissure. 



In the embryo of 13 miUimeters the parotid has advanced but httle 

 upon the conditions just described. Its site (Fig. 31), however, and 

 the proportions of the mouth have altered somewhat. The buccal 

 sulcus craniad of the orbital angle has lengthened relatively to a con- 

 siderable degree. The parotid {12) no longer is attached at the post- 

 angular bend, but at a considerably more caudal point. There is a 

 long orbitoparotid interval {15), which is, in part, due to the shortness 

 of the cranial process of the inclusion in this embryo. From the in- 

 ception of the proliferation, the flange of the parotid has been growing 

 broader in the region of the bud, while its caudal border has gradually 

 become transverse, until now the anlage has the form of a nearly 

 equilateral triangle with an enlargement at the free angle and along 

 the lateral border, which is somewhat greater than in the 12.5 milh- 



