THE NASAL REGION IN EUTAENIA. 399 



The contents of the nerve-bundles near their origin from the olfac- 

 tory lobes have a gelatinous appearance, with delicate lines to indi- 

 cate a division into fibres. Each bundle is provided with a thin 

 cellular sheath, which in cross sections is seen to strike in to form 

 still smaller bundles. The fibres which appear moi'e distinctly some 

 distance down the bundle are non-medullated, but provided with 

 a distinct sheath in which are to be observed here and there 

 spindle-shaped cells, giving often the appearance of swellings oh 

 the course of the fibre. In the immediate neighbourhood of the 

 sensory stratum either of the Organ of Jacobson or of the nasal 

 cavity, these appear to be wanting. The diameter of the nerve 

 threads here compared to those of the bundles farther iip, would seem 

 to indicate that these are primitive fibrils formed by the division of 

 the contents of the main fibres. These primitive fibrils, if they are 

 such, show no varicosities and give no evidence of any sheath like 

 that possessed by the main fibres beyond having a sharply defined 

 boundary. These fibrils are seen in such a condition when the sen- 

 sory cells are pencilled out from cellular columns, leaving only a few 

 fibrils. They terminate as far as I can make out from my preparations 

 at the central processes of the censory cell. The process and the 

 fibril are of equal diameter. In sections from the embryo the fibrils 

 appear to end in the nuclear portion of the sensory cell, and then a 

 central process is not percievable. It is impossible to say whether 

 the latter is a structure distinct from the nerve fibril ; on the other 

 hand, I have no hesitation in saying that the both are continuous. 



The bundles may divide for both the Organ of Jacobson and the 

 nasal cavity. Those for the former are arranged in a fan-shaped 

 fashion. The smaller bundles for the nasal cavity strike in at every 

 ano-le through the mucous stratum, bending around capillaries and 

 crypts of Bowman till they reach the sensory stratum. 



The nasal cavity, in front of its anterior opening, is of the shape 

 represented in Fig. 6. The groove to be found on its floor here 

 runs backward through the opening on the cheek posteriorly. 

 (Fig. 7, gr.) Behind this the passage takes a V form, whose 

 lumen the turbinal ingrowth tends more and more to diminish, 

 and is practically divided by it into two channels, one. the upper 

 nasal chamber, to a great extent lined by the olfactory mem- 

 brane, and communicating over the rounded edge of the turbinal 



