OLFACTORY ORGAN 



{05 



It is supported by an outward 

 cartilaginous septum nasi 

 which arises from the eth- 

 moid, as well as by other 

 secondarily independent car- 

 tilages (ali-nasals) which 

 were primarily continu- 

 ous with the general carti- 

 laginous wall, but become 

 differentiated from the 

 latter in various ways in 

 accordance with the varied 

 functional adaptations which 

 the outer nose undergoes. 

 Thus it may be provided 

 with a special valvular ap- 

 paratus for closing the nos- 

 trils (aquatic Mammals) ; or 

 may grow out to form a 

 longer or shorter trunk 

 provided with a complicated 

 musculature (Mole, Shrew, 

 Pig, Tapir, Elephant), and, 

 by means of its abundant 

 nerve-supply, serve as a 

 delicate organ of touch and 

 even as a prehensile appar- 

 atus. 



n 



extension of the nasal bones and by the 



FIG. 163, c. TRANSVERSE VERTICAL SECTION 



THROUGH THE NASAL CAVITY OF MAN. 



/, //, ///, inferior (maxillary), middle, and 

 superior turbinal ; a, b, c, inferior, middle, 

 and superior nasal passage ; S, septum 

 nasi ; J, J, position of rudimentary Jacob- 

 son's organs, which are situated nearer the 

 floor of the cavity than is indicated in the 

 figure ; *, point at which the naso-lachrymal 

 duct opens ; t, entrance into the maxillary 

 sinus (C.m) ; SL, ethmoidal labyrinth ; 

 ffG, hard palate ; C.cr, cranial cavity ; 

 J/, maxilla ; Or, wall of orbit. 



D 



E 



FIG. 164. VARIOUS FORMS OF THE MAXILLO-TURBINAL OF MAMMALS. 



A , double coil ; B, transition from latter to single coil, E, F ; C, transition from 

 double coil to the dendritic form D. (After Zuckerkandl. ) 



JACOBSON'S ORGAN. 



By the term " Jacobson's organ " is understood a paired accessory 

 nasal cavity which in an early embryonic stage becomes differen- 

 tiated from the nasal chamber, and which is supplied by the 

 olfactory and trigeminal nerves; it communicates with the mouth 

 by a special aperture. 



