DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 247 



solid slender branch was directed mesad, craniad, and slightly ventrad, 

 from the mesal side of the duct, close to the border of the masseter, 

 as though seeking its ental surface. A short distance craniad a second 

 small sprout was found, also directed mesad. Both arise in relation 

 to the cranial third of the muscle. In embryo No. 144, of 31 milli- 

 meters length (Fig. 105, gg), again on the left side, two recurrent sprouts 

 are present. They are subequal and soHd, scarcely enlarged at their 

 extremities, and arise close together from the ventromesal aspect of 

 the parotid duct, opposite the middle third of the masseter. They 

 correspond both in their relation to the masseter and to the parotid 

 duct to the variant ventral accessory lobules of the adult cat (Part V, 

 Fig. 5- 6, 7). 



The duct gradually changes its inframuscular for a transmuscular 

 position. The proximal segment of the duct is first affected. In the 

 25 millimeter embryo this has a straight course from the mouth to 

 the border of the masseter, which it crosses near the junction of its 

 lower and middle thirds. From this point it inclines ventrad in a gentle 

 curve. In the 35 millimeter embryo (Fig. 106) the duct has a longer 

 straight segment, which extends a little obUquely over the first third 

 of the muscle, crossing about halfway between the dorsal and ventral 

 borders. It then curves ventrad; its branches are retromasseteric, the 

 lowermost at the level of the ventral border of the muscle. The 

 duct is straight, but slightly inclined ventrad in its whole course in 

 the embryos of 51 and of 70 millimeters, and placed nearer the dorsal 

 than the ventral border of the muscle. 



The masseter has increased its sagittal dimensions markedly during 

 this process, and no doubt its lengthening may play a role in taking 

 up the slack in the duct, but from the nature of the displacement of 

 the duct, which is progressive craniocaudad, it would seem that changes 

 in the general topography of the region, perhaps associated with the 

 development of the alveolar processes and the consequent modifications 

 of the cheek and masseter, must be reckoned with as factors in this 

 change of level. 



Throughout development the duct presents a pale center in section ; 

 here the cells stain faintly, and have pyknotic nuclei. Their pallor 

 increases in later stages and often simulates a lumen. When an 

 actual lumen is formed, these cells disappear. A lumen is present 



