DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 253 



the embryos where the inclusions are free, a remnant of the flange may 

 be found attached to the buccal sulcus opposite the cranial half of the 

 vein or in a prevenous position. Evidently the fold has been of aver- 

 age length, but the inclusion after separation has shortened. The rate 

 at wliich tliis is accomplished gives ground to infer that the inclusion 

 is really under some tension from growth of the sulcus, to which it is 

 attached only by its extremities. This may also be a factor in its 

 ventral displacement during this period. In the 21 milhmeter em- 

 bryo the cranial process is already rudimentary and separated by an 

 interval of 107 /^ from the vein ; in older embryos it can scarcely be 

 said to be present, the inclusion terminating with a rounded knob, 

 the pars lata, near the orbital angle. 



It thus appears that the middle of the deep facial vein is passed by 

 the majority of orbital inclusions, and that the postvenous position, 

 while possibly in some cases primary, is, as a rule, acquired by reduction 

 of the cranial process. The vein may, therefore, serve as the normal 

 caudal limit of the orbitoparotid interval, subsequent to the separation 

 of the inclusion and until the sprout of the first orbital is formed. This 

 sprout at its inception is found in the plane of the deep facial vein, but 

 in all of our material lies craniad of the tip of the orbital inclusion. 

 The time of its appearance varies ; it may be present in embryos of 

 18.5 millimeters, but may be absent even as late as in 20-21 milli- 

 meter embryos. It is clear that the sprout is situated close to the 

 junction of the secondary buccal furrow with the superior alveobuccal, 

 but it is hardly possible, and perhaps hardly desirable, to make a 

 definite assignment of it to either. In one or two cases when the sprout 

 was present, the sulcus of the interval showed a slight flange prevenous 

 in situation. If this could with certainty be interpreted as a remnant 

 of the flange of attachment of the cranial process, the orbital sprout 

 would have to be assigned to the secondary buccal sulcus. But the 

 flanges in question may equally well be ascribed to a remnant of a 

 previously complete orbitoparotid bridge, or even to the postglandular 

 flange of the parotid. 



If the deep facial vein be taken as the average caudal limit of the 

 interval, the cases of prevenous extension of the inclusion must be con- 

 sidered as encroachments u]x)n its territory on the part of the orbital 

 fold wliich, as has been stated, may advance within 57 /it of the parotid. 



