418 



SPECIAL HISTOLOGY. 



however, some were also incrusted ; and in the deeper parts of 

 the epithelial layer itself, there were scattered, smaller, simple 

 or aggregated concretions, like " brain-sand" in miniature. 



The proper olfactory mucous membrane of all the divisions of 

 the organ, occupies only the uppermost parts of the septum 



and of the walls of the proper 

 nasal fossce, where the superior 

 spongy bones are situated, to a 

 distance of about % — \" down- 

 wards from the lamina cribrosa. 

 It is distinguishable, even by 

 the naked eye, from the con- 

 tiguous ciliated membrane, by its 

 greater thickness and its colour, 

 which is sometimes yellowish, 

 as in Man, the Sheep, and Calf; 

 sometimes yellowish-brown or 

 brown, as in the Rabbit and 

 Dog ; and, when examined micro- 

 scopically, it is seen to be bounded 

 by a tolerably well-defined, toothed 

 or undulated border. The dif- 

 ferences of the structure depend 

 upon the condition of the epithelium, the occurrence of 

 numerous peculiarly constructed glands, which I shall term 

 " Bowman's glands," and upon the relations of the nerves. 

 The epithelium is not ciliated, of which I have most fully 

 satisfied myself, not indeed in Man, in whom I have never yet 

 met with the epithelium of the true olfactory region in a 

 perfect condition, although the ciliated epithelium occurred 

 frequently enough still in a state of vibration, but in the 

 animals just named. It is also much thicker, so that in the 

 Sheep, in which the ciliated epithelium is O03'", it measures 

 O05'", and in the Rabbit, the one is 004'" thick, and the 

 other 007'". Notwithstanding this thickness, which is con- 



Fig. 312. From the nasal mucous membrane of the Sheep, x 150 diam. 1, from 

 the regio olfactoria, transverse section of the mucous membrane : a, epithelium 

 without cilia ; b, olfactory nerves, with a dividing, pale, nucleated fasciculus ; c, one 

 of " Bowman's glands ;" d, its orifice. 2, ciliated epithelium of the Schneiderian 

 membrane. 



