ORGAN OF SMELL IN MAMMALIA. 



217 



In Man the number of olfactory nerves varies from fifteen to 

 twenty: after traversing the cribriform plate, they divide into 

 two chief sets, ( septal ' and ( turbinal,' and ramify between the 

 periosteum and the pituitary membrane before terminating on the 

 latter. The septal nerves, fig. 158, , are about twelve in 

 number, are quickly resolved into brushes 

 of filaments, which unite together to form 159 



plexuses, and send off branches forming 



158 



Branches of the olfactory and nasopalatine nerves on the 

 septum of the nose. xciv. 



Alar cartilages, human tiose, 

 xciv". 



finer plexuses, traceable to near the base of the septum. The 

 posterior fourth of the septal membrane is chiefly supplied by the 

 nasopalatine nerve, b. The ' turbinal ' or labyrinthic olfactory 

 nerves are more numerous, rather smaller, and more plainly 

 anastomotic in their course over the upper and middle ttirbinals, 

 lying in grooves of the former, and extended chiefly upon the 

 inner and lower front of the midturbinal ; a few combine with 

 that part of the nasopalatine which supplies the lower part of the 

 middle turbinal. The lower turbinal is almost exclusively sup- 

 plied by a branch of the ( nasopalatine.' The main charac- 

 teristic of the human organ of smell is the prominence of the 

 fore-part of the chamber, having the nostrils on its lower surface, 

 and constituting the feature emphatically called the f nose,' figs. 

 159, 161. The formative fold of integument is supported by 

 eleven cartilages, of which one is medial, the others lateral, 

 in live pairs. The medial or ( septal ' cartilage, fig. 160, is usually 

 triangular, with three unequally curved margins : the upper one, 



