2 26 DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



have indications of a possible continuity of the folds, a condition oc- 

 casionally reaUzed in the cat, as appears in the next embryo. 



In this, No. 263, likewise of 12 millimeters, the fold of the parotid 

 has much resemblance to that just described. - It gradually broadens 

 to a ma.ximum and then diminishes somewhat, but is, nevertheless, 

 continued as a perfectly definite though narrow flange to the cranial 

 process of the orbital inclusion. An orbitoparotid interval, therefore, 

 does not e.xist ; the intermediate flange wlaich has replaced it may be 

 called the orbitoparotid bridge. Apart from its continuity with the 

 parotid, the inclusion is of the usual conformation. In tliis embryo 

 (Fig. 48) the parotid bud makes its appearance as a slight enlarge- 

 ment of the lateral border of the flange at its point of maximum 

 breadth. The axial line of periderm cells, the gradual opening of 

 the fissure mesad, the uniform curve of the dorsal surface of the 

 anlage, and the dense area of mesenchyme ventrad, are well shown in 

 this section. 



In all of these embryos the parotid fold is situated near the post- 

 angular bend of the buccal sulcus. On account of this change in the 

 curvature of the sulcus, section counts are of little or no value in deter- 

 mining the relation of the anlage to the angulus oris ; all that can be 

 said is, that the more developed folds appear to be situated farther 

 caudad, undergoing from the time of their appearance a relative 

 displacement in tliis direction. This becomes perfectly clear in older 

 embryos (Figs. 41, 43-45)- 



The anlage of the masseter is represented at the stage of 12 milli- 

 meters by a dense area in the mesenchyme, which craniad diminishes 

 and becomes indistinguishable from the tliickening destined to form 

 the zygoma. The ventral border of the anlage slopes ventrad and 

 caudad and passes the buccal sulcus in the orbitoparotid interval, 

 here coming closer than elsewhere to the oral epithelium. The parotid 

 flange lies ventrad to the cranial prolongation of this anlage ; but with 

 reference to its intersection with the buccal sulcus it is promasseteric. 

 On account of this relation a hne of least resistance is determined for 

 the sprout in a ventrocaudal direction along the sloping border of the 

 masseter, which in this respect serves to divide the buccal sulcus into 

 a promasseteric segment, the derivatives of which grow along the 

 ventral border and lateral surface of the muscle, and an entomasse- 



