THE NASAL REGION IN BUTAENIA. 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 more 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 on 
the course of the fibre. In the immediate neighbourhood of the 
sensory stratum either of the Organ of Jacobson or of the nasal 
eavity, these appear to be wanting. The diameter of the nerve 
threads here compared to those of the bundles farther up, 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 distirict 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 
angle through the mucous stratum, bending around capillaries and 
erypts 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 
