DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 213 



nerve is becoming separated from the mouth in a caudolateral direc- 

 tion, and has no longer the value of a relatively fixed point in the chang- 

 ing topography of the buccal sulcus. 



We may make use of the buccomasseteric crossing and the orbital 

 inclusion to investigate the nature of the formation of the preorbital 

 segment of the buccal sulcus. The following measurements, all of 

 the right side, are section counts reduced to micra. On account of 

 the obliquity of the buccal sulcus they have no absolute value, but 

 since the obliquity does not vary greatly in the several embryos, and 

 the planes of the sections correspond fairly well, they suffice for a 

 rough comparison and throw some Ught on the complex conditions 

 of growth in this portion of the oral cavity. The position of the second 

 and third embr>'os in this small series requires a word of explanation. 

 They are Utter mates corresponding closely in general development. 

 One, however, measured 9.5 milhmeters, the other 10 millimeters. Both 

 are intermediate in development between a 10.5 millimeter embryo, 

 No. 1 20, and that of 1 1 millimeters. No. 213, all of which were measured 

 under identical conditions. Some variations in the degree of curva- 

 ture of the embryos is probably the explanation of the disorder of the 

 series. As similar discrepancies occur in several of our litters, one is 

 disposed to wonder whether an estimation of volume might not form 

 a more accurate criterion of development than linear measurement. 

 Thus quaUfied the dimensions in question follow : — 



The first four embryos show a progressive increase of the distance 

 between the buccomasseteric nerve and the angulus oris, while the 

 orbital inclusion remains of approximately the same size. The pre- 



