(318 



Jacob Parsons Schaeffer. 



Chganitn z'omeyo- 

 nasii/r (Jacobsoni) 



l-atcral nasal j^ 

 process 



AfaxiUai'v 

 process 



Afiilial nasal process 



I'limilire rhuuiiu 

 (potilion for) 



NarU 



Primitive palate 



2 



Fig. 1 (X 30) Drawing of a reconstruction of portion of the head of an embryo 

 aged approximately 35 days (Hmnan embryo, No. 6, Cornell University series, 

 slides 50-57 inclusive). The figure represents a caudo-ventral view of the recon- 

 struction. 



Note the wide separation of the nasal fossae at this time, and that the fossae do 

 not communicate with the mouth cavity. The maxillary and the medial nasal 

 processes have fused, thus shutting off the nasal pits from the mouth cavity. The 

 lateral nasal processes have not yet fused with the medial nasal processes. The 

 external nose has not yet taken on any definite shape. Note the points for the 

 jirimitive choanae and the extent of the primitive palate. 



Fig. 2 (X 45) Drawing of a I'econstruction of the left nasal fossa. The recon- 

 struction is from the same embryo as that in fig. 1, and the plane of section is indi- 

 cated by the line drawn over the left nasal fossa in fig. 1 . Note the very simple 

 lateral nasal wall at this stage of development and compare it with the medial wall. 

 In a short time the lateral wall becomes much more complex and the medial wall 

 relatively less so. 



