396 



ELEMENTAR Y ANA TO MY. 



[LESS. 



separated, and secondarily connected with the upper part of 

 the hyoidean visceral arch, 



-A 



FIG. 347. DIAGRAM ILLUSTRATING THE DIFFERENT DEVELOPMENTS IN SAURO- 

 PSIDANS AND ICHTHYOPSIDANS OF PARTS WHICH IN MAMMALS BECOME THE 

 AUDITOKY OSSICLES. 



(After Huxley.) 



No. i, the parts in Man ; No. 2, the parts in the Lizard Sphenodon ; No. 3, the 

 parts in the Cod. 



a, malleus, or quadratum ; a', the segment of it called os articulare ; a", the 

 segment of it called meta-pterygoid ; 3, incus in the Lizard Sphenodon that 

 part of the continuous cartilage which answers to man's incus in the Cod, 

 the hyo-mandibular ; c, the stapes columella auris in Sphenodon ; d, the 

 dentary piece of the lower jaw ; s, stylo-hyoid, or, in Sphenodon, that part of 

 the continuous cartilage which answers to it ; s , the stapedius muscle ; s", 

 the stylo-hyoid muscle; bh, the basi-hyal, or body of the hyoid : h, the 

 corniculum of the hyoid in the Cod, called cerato-hyal ; y, symplectic. 



The external ear, or pinna, may be entirely wanting, as in 

 the Whales and in all below the Crocodiles, in which latter 

 animals it is represented by a slight fold of skin. 



On the other hand, its proportions may greatly exceed 

 those of man, and, in the little Bat Plecotiis, may equal 

 in length the entire trunk. Moreover, 

 the tragus may be (as in the Insectivo- 

 rous Bats) so largely developed as to 

 look like a second pointed ear standing 

 up inside the normal one. 



A lobule is almost peculiar to man, 

 though a rudiment of it is found in the 

 Gorilla, 



24. The portio dura of the SEVENTH 

 NERVE (i\\Q facial] arises from the pos- 

 terior division of the hind-brain, appear- 

 ing at the posterior margin of the 

 pons Varolii, 'It enters the internal 



auditory meatus, and, piercing the petrous part of the tem- 

 poral bone, bifurcates, and one part comes out at the stylo- 

 mastoid foramen, This part is distributed to the ear-scalp and 





FIG. 348. HEAD OF THE 

 COMMON LONG-EARED 

 BAT (Plecotusauritus). 



t, the tragus of each ear. 



