DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 235 



of the parotid appears to be one of proliferation, not only as regards 

 the free sprout in the mesenchyme, but also in the formation of the 

 proximal segment of the duct. From this standpoint the flange 

 becomes merely auxiliary to the process of proliferation, which it 

 serves as a guide in determining the direction of its growth and perhaps 

 also, arguing from the early appearance and rapid enlargement of 

 this and other sulcal glands, in some way contributes to accelerate 

 its development. 



While the evidence derived from the structure of the anlage seems 

 adequate to establish the fact of the advance of the parotid duct, 

 the attempt to estimate the degree of the process is encumbered with 

 difficulties. The buccal sulcus lengthens by cranial increment, 

 and the rate of this process being greater than that of the advance 

 of the parotid, the distance between it and the angulus oris is pro- 

 gressively increased. Measurements from this point, therefore, are 

 of no assistance. Nor are the measurements from the buccomas- 

 seteric crossing more satisfactory. They show merely an increase 

 in the distance from the nerve to the parotid, without enabling us to 

 determine how much of the increment is to be assigned to the sagittal 

 lengthening of the oral cavity, and how much to the displacement of 

 the anlage. We are, therefore, forced to rely upon indirect evidence. 

 In the 13.5 millimeter embryo (Fig. 34, 17) a variant sprout was 

 formed at the junction of the parotid with the oral epithehum, the 

 orbitoparotid element. Subsequently this may retain its connection 

 with the oral epithehum or with the parotid duct. In cases of the 

 latter ty[De we have a means of estimating the amount of duct formed 

 by constriction. In two cases this element was found attached to the 

 parotid as far caudad as the border of the masseter. This condition 

 will be described more fully in the sequel. It indicates that the whole 

 promasseteric portion of the duct is to be ascribed to the process of 

 constriction and not to the free distal growth of the sprout. The 

 promasseteric segment of the parotid duct has a length of about one 

 centimeter in the adult. 



Thus far we have been considering the sagittal advance of the 

 parotid. Coincidently it undergoes a displacement in the transverse 

 plane, which carries it away from the buccal sulcus along its dorsal 

 wall mesad towards the dental ridge. The degree of the shift is not 



