602 NASAL MUCOUS MEMBRANE. [sect. 235. 



conducting canals, concerned simultaneously in the function of 

 respiration, or, at least, are destitute of any direct relation to the 

 olfactory sense. 



The above-mentioned hard structures do not present much 

 worthy of remark ; and of the bones it needs only to be men- 

 tioned, that in the ethmoid at its thinnest spots, the bony tissue 

 consists only of a matrix and lacunas, without Haversian canals. 

 The cartilages of the nose are true cartilages, and bear most re- 

 semblance to that of the larynx, except that the contents of their 

 cells are mostly pale and destitute of fat, the cell-walls but little 

 thickened, and the matrix finely granular. Beneath the peri- 

 chondrium of these cartilages there also lies a layer of flattened 

 cells, which attains a thickness of 0024" upon the septum ; while 

 in the interior the cells are more roundish, larger, and arranged in 

 rows, in the direction of the thickness of the cartilaginous plate. 



Of the coverings of these parts, we may first make mention of 

 the external skin of the nose; this is characterised by a thin 

 epidermis (o'024'" to 0'032'"), a tense cutis, \'" thick, with small 

 undeveloped papillae (Vo" to -gV"), and fine hairs; and also by a 

 dense adipose tissue, one line thick, intimately united with the 

 cartilages, and containing large sebaceous glands extending into it, 

 with small sudoriparous glands, ^~ " to ^" . This external skin 

 extends with its sebaceous glands, and provided with thicker hairs 

 (vibrissas), for some distance into the nasal cavity, almost up to 

 the place where the external nasal cartilage ceases, and then passes 

 imperceptibly into the mucous membrane of the olfactory organ; 

 and this mucous membrane, is continued from hence to form the 

 lining of all the remaining spaces, though it does not present the 

 same characters everywhere. According to Todd and Boicman's 

 discoveries, which I can fully confirm, it is divided, in animals, into 

 a ciliated and non-ciliated part, the latter of w r hich is limited to 

 the uppermost parts of the proper nasal cavities, where the olfactory 

 nerve is distributed; this should, therefore, be called the olfactory 

 mucous membrane in the stricter sense, while the other may retain 

 the old name of Sclineiderian membrane. 



If we begin by inspecting the latter membrane — the ciliated 

 portion of the nasal lining, we find that its structure is not every- 

 where the same ; and we may conveniently distinguish the thicker 

 glandular mucous membrane of the proper nasal cavity from the 

 thinner one lining the accessory cavities, and the interior of the 

 turbinate bones. In both places, the epithelium is of the lamel- 

 lated ciliated kind, similar to that of the larynx (fig. 247, 2), 



