290 



DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 



The proliferation and constriction advance steadily from the 

 lingual crossing, but the constriction more rapidly. In the 18 milli- 

 meter embryo the proliferation has gained upon the sulcus, which 

 has made no advance upon the 17 millimeter embryo. Here, again, 

 we have evidence that the formation of the duct is by a process inde- 

 pendent of the sulcus, since it may lengthen while the sulcus is at a 

 standstill. 



During the period between 20 and 30 millimeters the duct continues 

 to advance by the formation and separation of a keel, and during 

 the latter part of tliis period at a rate sufficient to gain upon the length- 

 ening of the region and to approach the cranial end of the lingual 

 sulcus. In the 51 milUmeter embryo the attachment is circular; 

 there is no sign of a keel, and the duct, so far as intrinsic processes are 

 concerned, has come to rest. 



The following measurements show a progressive and absolute 

 advance from the Ungual crossing. The distance between the keel 

 and the confluence of the sulci indicates a fluctuating balance of 

 growth between the region as a whole and the proliferation of the keel, 

 incKning now to favor the one, now the other, but finally the growth 

 of the keel predonunates and the duct makes a relative as well as an 

 absolute advance. 



The constriction on the whole gains upon the proliferation, and the 

 keel, which indicates the balance between these two processes, is 



