104 F. W. STEWART 



ing to the general contour of the adjacent part of the olfactory 

 sac. The proliferation again is confined to the medial aspect of 

 the sac. In the ganglion-like aggregate, numerous cells are 

 distinguishable with darkly staining cytoplasm. They are too 

 closely packed to enable one to follow processes very distinctly. 

 In general, the nuclei appear more rounded than those just 

 freed from the confines of the olfactory epithelium. It would 

 seem to be this structure which Dollken ('09) has termed the 

 ganglion terminale. That this recognition by Dollken is scarcely 

 accurate is 'noted by Johnston ('13). The subsequent fate of 

 the cells of this aggregate will be traced in later stages. 



Figure 3 gives some idea of the relation of the two trigeminus 

 strands — ophthalmicus (o) and maxillaris {m) — to the olfactory 

 epithelium. In a fortunate section each was photographed 

 at the point where it most nearly approached the epithelium. 

 The maxillaris appears more extensive in the photograph than 

 it actually is, since its foremost tip extends into elongated mesen- 

 chymal cells surrounding a vascular channel. Its anterior limit 

 is marked by an {x). Although a pyridine-silver preparation 

 might possibly show fibers extending beyond this point, the 

 extent of migrating cell elements is believed accurately depicted 

 in the photograph. So far, then, the proliferation from the 

 epithelium of the olfactory sac is independent of any contribu- 

 tion of trigeminus origin. 



Following stages (12 days 18 hours) do not show sufficient 

 advancement to merit separate description. The mass of cells — 

 'olfactory ganglion' — is merely increased in size. It occupies 

 the posterior part of the septal territory'-, being quite closely 

 molded to the olfactory sac. Vom Rath material does not show 

 as yet any olfactory fila entering the brain at this stage, although 

 they approach it quite closely. 



. Disregarding thirteen-day stages and passing to the considera- 

 tion of embryos of the 13-day-4-hour litter, of which three are 

 available, the following facts may be noted: The olfactory 

 epithelium is in contact posteriorly with the oral epithelium in a 

 bucco-nasal membrane — exceedingly thin, but as yet unruptured. 

 The fibrous strands originating from the olfactory epithelium, 



