OKGAN OF JACOBSOX. 



143 



The nerves ramify so as to form flattened tufts, the filaments of which, spreading 

 out laterally and communicating freely with similar offsets on each side, form a 

 close plexus, with elongated and narrow meshes. 



Fig. 162. NERVES OF THE SEPTUM NASI, SEEN PROM THK RIGHT SIDE. 



Hirschfeld and Leveille.) 



(From Sappey, after 



I, the olfactory bulb ; 1, the olfactory nerves passing through the foramina of the cribriform plate, 

 and descending to be distributed on the septum ; 2, the internal or septal twig of the nasal branch of 

 the ophthalmic nerve ; 3, naso-palatine nerves. 



In their structure the olfactory nerve-fibres differ much from the ordinary 

 dark-bordered fibres of the cerebral and spinal nerves : they possess no medullary 



Fig. 163. NERVES OF THE OUTER WALL OF THE NASAL 

 FOSS.E. (From Sappey, after Hirschfeld and 

 Leveille. ) f 



1, network of the branches of the olfactory nerve, 

 descending upon the region of the superior and middle 

 turbinated bones ; 2, external twig of the nasal nerve ; 

 3, spheno -palatine ganglion ; 4, ramification of the 

 large palatine nerve ; 5, small, and 6, external palatine 

 nerves ; 7, branch to the region of the inferior tur- 

 binated bone ; 8, branch to the region of the superior 

 and middle turbinated bones ; 9, naso-palatine branch 

 to the septum cut short. 



sheath, but are axis-cylinders provided with 

 a distinct nucleated sheath, much more 

 distinct than that of the fibres of Eemak 

 and with nuclei at less frequent intervals 

 (fig. 164). 



The greater part of the mucous mem- 

 brane of the nasal fossae is provided also 



with nerves of common sensibility, derived from branches of the fifth pair : the 

 distribution of these has already been described. They appear to end amongst the 

 epithelium cells in arborisations which have been noticed by several observers in 

 preparations made by the silver chromate method. 



The Organ of Jacobson. In the anterior and lower part of the nasal septum 

 a small aperture may sometimes be seen opening obliquely on to the surface of the 

 mucous membrane slightly above and in front of the orifice of the nasopalatine canal 

 (see fig. 157). This aperture leads into a minute canal which passes backwards for 

 a short distance along the septum to terminate blindly a few millimeters from the 

 orifice. The canal, which is lined with epithelium continuous with that of the 



