DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 259 



involve the whole transmuscular portion (Part V, Fig. 13). In view 

 of these facts a sharp distinction can hardly be maintained between 

 the accessory parotid lobules and orbitoparotids draining into the 

 main duct, while the latter through the sprout of angular position 

 are serially continuous with those that arise from the oral epithehum 

 in the course of the orbitoparotid interval. 



These constitute the third class of orbitoparotids, which are by far 

 the most numerous in our series and the only ones present in embryos of 

 more than 20 millimeters length, although in the adult representatives 

 of the other types are found occasionally (see Part V, p. 164). They 

 are most numerous close to the parotid, not infrequently as far caudad 

 as the middle of the interval, rare in the third quarter, while none was 

 observed in the fourth. They are frequently attached to small crests, 

 but whether these are remnants of the orbitoparotid flange or prolifera- 

 tion keels cannot in individual cases always be determined. Some 

 certainly are remnants of the flange, being pointed at their distal 

 extremity and constricted at the attachment of the sprout. Others 

 are rounded at their free margin and constricted at their attachment 

 only in their caudal sections. That these are keels of proliferation 

 and serve to advance their sprouts seems probable, from the retention 

 of the angular position in embryo No. 80 and the greater frequency of 

 the element in the cranial half of the interval even in late stages. The 

 keels vary in length from 27 to 80 fi. The sprouts may follow either 

 the parotid or the orbital path, the more cranial inclining to the former, 

 the more caudal to the latter direction of growth. From the greater 

 frequency of the cranial position the parotid line is far the more usual. 

 In two cases what looks to be a sort of vacillation on the part of the 

 sprout occurs. In embryo No. 252 of 19 millimeters, a sprout arising 

 from the oral epithehum a short distance caudad of the parotid ap- 

 proaches that duct until no mesenchyme can be seen between them, 

 but bends mesad in its caudal segments towards the buccal sulcus 

 without, however, coming very near it. An interesting case occurs in 

 the 70 millimeter embryo on the left side (Fig. 117). Arising from the 

 stomal ridge midway between the parotid and first orbital orifices, the 

 sprout extends caudad as a soUd slender rod of cells for -a distance of 

 420 /i, diverging very slightly from the oral epithelium. It lies laterad to 

 the first orbital duct, extending beside it to a point 1 20 m caudad of the 



