ELEMENTARY ANATOMY. 



[LESS. 



The true OLFACTORY NERVES are filaments which pass from 

 the lobes to the inner surface of the olfactory organ. In man 

 and Mammals they pass through the foramina of the cribri- 

 form plate to the mucous membrane, investing the spongy 

 bones (or lateral ethmoid and turbinals) as described in 

 Lesson VIII. 13 of the "Elementary Physiology." 



Pa, 



FIG. 332. VERTICAL LONGITUDINAL SECTIONS OF THE NASAL CAVITY. 



The left-hand figure represents the outer wall of the right nasal cavity ; the right- 

 hand figure the left side of the middle partition or septum of the nose, which 

 forms the right wall of the left nasal cavity. 



/, the olfactory lobe and its branches ; V, branches of the fifth nerve ; Pa, the 

 palate which separates the nasal cavity from that of the mouth; ST, .the 

 superior turbinal bone; MT, the middle turbinal; IT, the inferior turbinal. 

 The letter / is placed in the cerebral cavity. The partition on which the 

 olfactory lobe rests, and through which the filaments of the olfactory nerves 

 pass, is the cribriform plate. 



An essentially similar arrangement to that in man exists in 

 all Vertebrates above Fishes, except in those destitute of an 

 olfactory organ, as the Cetacea. The place of opening of 

 the posterior nares within the mouth 

 varies not only as before noticed in de- 

 scribing the skull, but the aperture may 

 be placed half-way down the throat, as 

 in Myrmecophaga. The singular elon- 

 gation of the nose in the Elephant has 

 also been adverted to in the Lesson on 

 the Muscles. Singular leaf-like expan- 

 F T G . 333 ._M E MBRANEDE- sions of membrane may be developed 

 VELOPED ON THE NOSE from the external skin of the nose, as 

 orTHBBAT-Sftffc&rwa i n the Horse-shoe Bats (Rhinolophus 

 and Megaderma, especially the latter 

 genus) and Vampires (Phyllostomd) ; 



and an extra median ossicle may be developed in the snout, 

 as e.g. in the Mole,, 



