DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 289 



considered fairly typical of their groups. The most variable measure- 

 ment was that of the length between the confluence of the sulci and 

 the lingual crossing. In this respect the embryos between 13.5 and 

 16 millimeters may be said to be perfectly lawless. The measurement 

 seems to bear Uttle relation either to the general development of the 

 mouth or of the submaxillary in particular. The embryos No. 223 

 and No. 216 were chosen because they coincided in this dimension, 

 which makes apparent the slight gain of the submaxillary attachment. 

 The 17 milhmeter embryo shows a well-marked advance of the anlage, 

 which, however, is not sufficient to offset the lengthening of the sulcus. 

 The separation has now begun to advance beyond the lingual crossing. 

 In embryos of 18-20 millimeters the constriction advances rapidly 

 though mievenly, but is sufficient to reduce the length of the keel, 

 gaining considerably upon the proUferative process. In these embryos 

 the frenulum has altered its shape. It no longer has a vertical border 

 rising from the confluence of the sulci, but has become a large cres- 

 centic fold concave craniad with cornua forming ridges on the ventral 

 surface of the tongue and on the floor of the mouth. Craniad of the sec- 

 tion in which the tongue becomes free, the plica mediana extends as a 

 chminishing ridge between the lingual sulci. The section in which the 

 tongue becomes free is here termed the frenular section, and as it under- 

 goes a relative displacement caudad it is not a useful point to measure 

 from, as the distance between it and the submaxillary diminishes by 

 its own displacement, as well as by the advance of the anlage. The 

 keel of the anlage reaches this section in the 28 millimeter embryo. In 

 the following measurements the confluence of the sulci at the extremity 

 of the plica mediana is again used in preference to the frenular section. 



