3 8o NORMAL HISTOLOGY. 



cochlear branch is distributed to the lower turn of the cochlea and anasto- 

 moses with the cochlear artery proper. The vestibular branch is distributed 

 to the lower part of the vestibule, including the lower part of the saccule and 

 utricle, to the crus commune and part of the semicircular canals, and to the 

 lower end of the cochlea. The macula of the saccule receives its arterial 

 supply from a blood-vessel which usually arises from the common stem of 

 the vestibulo-cochlear artery, or, more rarely, runs independently through 

 the whole internal meatus. A similar origin applies to the artery supplying 

 the nerve of the posterior ampulla. In the base of the spiral lamina the 

 arteries are connected by capillary loops especially in the lower turn of the 

 cochlea. One or more spiral vessels are often seen under the tunnel of Corti 

 within the tympanic covering of the basilar membrane. The region of the 

 stria vascularis and prominentia spiralis is especially well supplied with 

 blood-vessels. Those seen in the scaia tympani are principally veins, while 

 a larger number of arteries are found in the scala vestibuli. The blood- 

 supply of the lower turn of the cochlea is much more generous than that of 

 the others. 



The veins from the cochlea include: (i) the vein of the vestibular aque- 

 duct, which collects the blood from the semicircular canals; (2) the vein of 

 the cochlear aqueduct, which collects from the whole cochlear canal through 

 the anterior, posterior and middle spiral veins and from most of the vestibule 

 through the anterior and posterior vestibular veins; and (3) the venous plexus 

 of the inner auditory canal, which receives the large central cochlear vein. 



THE NOSE. 



Although only a small part of the nasal chambers is occupied by the 

 peripheral olfactory organ in man, the greater part forming the beginning of 

 the respiratory tract, comparative anatomy and embryology establish the 

 primary significance of the nasal groove and its derivations as the organ of 

 smell, the relation of the nose to respiration being entirely secondary. The 

 nose, therefore, is appropriately grouped with the organs of special sense. 



The nose is conventionally divided into two portions: the external 

 nose, consisting of a framework of bone, cartilage and fibrous tissue, which 

 insures the maintenance of apertures for the passage of air, and the nasal 

 chamber, divided by a septum into the right and left nasal fossa and lined 

 by mucous membrane. The junction of the latter with the skin is marked 

 by a limiting ridge, the limen vestibuli, on the inner surface of the vestibule, 

 a short distance above the nostril. Apart from the unusually large seba- 

 ceous glands surrounding and the hairs (vibrissa*) guarding the nares, the 

 external nose presents little of especial histological interest. The description 

 of the external nose and of the complicated modelling of the nasal fossae fall 

 within the province of gross anatomy. The present consideration of the 

 nose, therefore, may be limited to the mucous membrane lining the nasal 

 chamber. 



THE NASAL MUCOUS MEMBRANE. 



Beyond the limit of the integument clothing the vestibule, the nasal 

 fossa is lined by mucous membrane continuous with that of the naso-pharynx 

 through the choanae. Since in addition to lining the tract over which the 

 respired air passes the nasal mucous membrane contains the cells receiving 

 the impressions giving rise to the sense of smell, it is appropriately divided 

 into a respiratory and an olfactory part. 



