278 THE ESSENTIALS OF HISTOLOGY. 



The corium of the olfactory mucous membrane is also very thick 

 (fig. 310). It contains numerous blood-vessels, bundles of the olfactory 

 nerve-fibres (which are non-medullated), and a large number of serous 

 glands known as Bowman's glands (b), w r hich open upon the surface by 

 fine ducts passing between the epithelium-cells. 



FIG. 310. SECTION OF OLFACTORY MUCOUS MEMBRANE. (Cadiat.) 

 a, epithelium ; 6, glands of Bowman ; c, nerve-bundles. 



STRUCTURE OF THE AUDITORY ORGAN. 



The external ear proper (pinna) is composed of elastic fibro -cartilage, 

 invested by a thin, closely adherent skin. The skin is covered by 

 small hairs, and connected with these are the usual sebaceous follicles. 

 In some parts e.g. the lobule there is a considerable amount of 

 adipose tissue ; and voluntary muscular fibres are in places attached to 

 the cartilage, and may therefore be seen in sections of the ear. 



The external auditory meatus is a canal formed partly of cartilage 

 continuous with that of the pinna, partly of bone. It is lined by a 

 prolongation of the skin and is closed by the membrana tympani, over 

 which the skin is prolonged as a very thin layer. Near the orifice the 

 skin has hairs and sebaceous glands, and the meatus is also provided 

 throughout the cartilaginous part with small convoluted tubular glands 

 of a brownish-yellow colour, which yield a waxy secretion (ceruminous 

 glands). They appear to represent modified sweat-glands. 



The tympanum is lined by a mucous membrane which is continuous 

 through the Eustachian tube with the mucous membrane of the 

 pharynx ; it is also prolonged into the mastoid cells. The epithelium 



