THE NOSE. 421 



Calf, send scattered dark-bordered primitive fibres in the 

 course of the branches of the olfactory nerves. The olfactory 

 nerve, in its tract and bulb, contains dark-bordered fibres 

 and nerve-cells, of which we have already spoken (vol. I, 

 p. 444). The nervi olfactorii, on the other hand, in Man 

 and in other Mammalia, even in the main trunks given off 

 from the olfactory bulb, present no white medullated fibres 

 at all, but are wholly constituted of pale, slightly granular 

 flattened fibres, 0*002 — 0-003"' wide with elongated nuclei, 

 which are closely adherent and retained in connexion by 

 common sheaths of connective tissue, which are somewhat 

 thicker and therefore whiter in the rami ad septum. With 

 respect to the origin of these fibres, which very closely re- 

 semble the embryonic nerve-elements, whether they are 

 derived from the olfactory bulb or from the cerebrum itself, has 

 by no means been as yet ascertained in Man, or in other 

 Mammalia, although, from the observations of Ley dig in the 

 1 Plagiostomata/ ('Beitrage/ p. 34, Tab. I, fig. 6), it is probable 

 that the former is the case. The termination of these nerves 

 is yet more doubtful. This much is readily seen, that the 

 nervi olfactorii, in their course in the mucous membrane of the 

 olfactory region, are gradually attenuated as they descend, in 

 consequence of numerous divisions at acute angles, and form a 

 plexus which may also, in Mammalia, be traced almost 

 throughout the olfactory region ; but shortly before reaching 

 its border, these plexuses are always lost to sight, nor is any 

 other indication of terminal branches presented ; so that, as 

 regards the main fact, I remain quite in the dark. At present 

 it appears to me most probable that the terminal distribution 

 takes place throughout the non-ciliated region, and above all at 

 its border; at any rate I have never yet been able to detect 

 the filaments of the olfactory nerves in the ciliated epithelium, 

 although they can be traced down to twigs of the size of 0005 — 

 O'Ol'". I have not seen the ganglion- globules on the inner 

 surface of the finer plexus mentioned by Valentin ('Nervenlehre/ 

 p, 303), and the rather strange looking " glands of Bowman," 

 might have been mistaken for such bodies. 



[In the investigation of the olfactory organ, the chief diffi- 

 culty arises from the softness of the epithelium, and on this 



