DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 249 



secondary formation parallel to the oral epithelium and lodged in the 

 stoinal ridge, and a distal portion, the product of its sprout, wMch is 

 dorsally directed towards the orbit. The change of direction corre- 

 sponds to the site of the early sprout, and should strictly be taken as 

 the caudal limit of the interval, which, therefore, in the adult corre- 

 sponds to the stomal ridge, from the parotid orifice caudad to its termi- 

 nation. The ventrolateral limit of the ridge is a furrow, the per- 

 sistent subparotid sulcus, while the ridge itself, occupying the interval 

 between the superior alveobuccal sulcus and this furrow, corresponds 

 in position to the obliterated portion of the buccal sulcus. In late 

 periods of development (70 millimeters and later) it becomes the site 

 of diffuse gland formation, as does also the subparotid sulcus. In the 

 adult the orifices of these glands are occasionally visible with a lens, 

 but their bodies are hardly more than microscopic. They appear, 

 further, to be highly variable. In view of their late appearance and 

 simple development they have been considered as ditTuse glands, and 

 as they are not associated with the buccal sulcus, but formed after its 

 reduction, they have been distinguished from the orbitoparotid 

 sprouts proper, which are sulcal in origin and early in development. 

 In the adult they open upon the stomal ridge between the parotid and 

 the first orbital gland, and in the line connecting their orifices. From 

 the standpoint of its derivatives, therefore, the interval is chiefl)- in- 

 teresting in this segment, for here alone are variants developed early, 

 here alone do they obtain even moderate size, and here also they may 

 lose their connection with the oral epithelium, or that of the parotid, 

 and become included in the mesenchjTne. The smaller, more caudal 

 derivatives, as well as by their secondary position the first three 

 orbitals, represent a link and largely efface the distinction between 

 the derivatives of the superior alveobuccal and those of the buccal 

 sulcus, so that here the elements of the two furrows come into actual 

 juxtaposition, and may form a gland mass (zygomatic or facial 

 "gland") usually of minute proportions, but which, nevertheless, in the 

 adult presents the same possibilities of confusion and the same diffi- 

 culties of interpretation, on other than embryologic grounds, as the 

 massa sublingualis of man. 



The orbitoparotid interval, thus defined, appears first in embryos 

 of 12 millimeters, with the establishment of the parotid flange at the 



