DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 245 



craniad with the remnant of the buccal sulcus, which is confined to 

 the postangular portion of the vestibule. In the 70 millimeter 

 embryo the stomal ridge is better defined, and at its ventral limit the 

 subparotid sidcus has deepened to a well-marked furrow (Fig. 114). 



The Sprout of the Parotid. — The inception of this sprout has 

 already been described in the embryos of 1 2.5-13.5 millimeters. The 

 direction of its distal growth is determined first by the position of the 

 flange and later mainly by the masseter muscle. The flange is itself 

 ^'entrolaterally inclined and, broadening caudad, causes its free 

 border to diverge caudolaterad from the buccal sulcus. The growth 

 of the sprout is in the resultant of these directions, ventrad, caudad, 

 and laterad. In embryos of 14 and 15 millimeters (Tigs. 41, 43-45) 

 the bud is retort shaped with a gradually lengthening neck ; its 

 direction is dominantly ventrad. It is first in relation with the facial 

 vein, which is grooved dorsad to receive it. About it is a plexus of 

 capillaries connected with the vein, which dorsad communicate with 

 the opthalmic vein through the deep facial vessel. While both limbs 

 of the ple.xus contribute to this connection, the communication in 

 the earlier embryos (13-15 miflimeters) is freest on the lateral aspect 

 of the parotid. In later stages the mesal loop is enlarged and the 

 lateral loses its connection with the orbital vessels. The deep facial 

 is formed mesad of the duct, while the lateral capillaries are organ- 

 ized into the superficial facial vein. This condition is established in 

 embryos of 16-17 millimeters, and is retained in the adult, where 

 the duct passes between these vessels, but separated from the deep 

 facial by the border of the masseter. The topography of the proximal 

 segment of the duct is shown in Figs. loo-ioi. 



In the most advanced of the 15 millimeter embryos the enlarged 

 fundus has passed beyond the facial vein and reached the sloping 

 border of the masseter. From tliis point its growth has a very definite 

 path, which the sprouts of the various embryos follow, apparently 

 without deviation, but at quite unequal rates. An idea of the difference 

 in size, which may obtain between parotids in embryos in which the 

 other oral derivatives are of corresponding development, may be 

 gained by a comparison of the two 15 millimeter embryos figured 

 (Figs. 44, 45). Similar discrepancies are present in all stages, some- 

 times even on the two sides of the same embryo. No attempt has, 



