OLFACTORY ORGAN 



205 



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 lios- 

 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. 



extension of the nasal bones and by the 



J 



n 



Fig. 163, c. — Tkansvekse Vertical Section 



THROUGH THE NaSAL C.VVITY OF MaX. 



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

 superior turbinal ; a, h, i:, 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 ; +, entrance into the maxillary 

 sinus (Cm) ; SL, ethmoidal labyrinth ; 

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

 J/, maxilla ; Or, wall of orbit. 



a 



J) 



E F 



Fig. 164. — Various Forms of the Ma.xillo-turbisal of Mammals. 



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

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



Jacobson's Organ. 



By the term " Jacobson's organ " is understood a jaaired 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. 



