XIII 



T'lIYLTM CHOHDATA 



o.Sl 



Insectivores and Rodents, nnd 

 the eyes ave imperfectly de- 

 veloped and functionless. 



The car of a Mammal is 

 more highly developed than 

 that of other Vertebrates, 

 both in respect of the 

 greater complexity of the 

 essential part — the mem- 

 branous labyrinth — and in 

 the greater development of 

 the accessory parts. A large 

 external auditory pinna, 

 snpported by cartilage, is 

 almost invariably present, 

 except in the Monotremata, 

 Cetacea, and Sirenia. This 

 is a Avidely open funnel, of a 

 variety of shapes in different 

 gronps, having the function 

 of collecting the waves of 

 sound. By the action of a 

 system of muscles it is 

 usually capable of being tur 



in Notoryctes among the Marsupials, 



J -v.i. 



— r. u. 



Fi(i. ]200. — Sagittal section tlirough the luisiil and 

 liucfal cavities of the human head. /, //, ///, 

 tiie three olfactory ridges formed by the turbinals ; 

 he, entrance to the mouth ; /(/. tf>ngue ; os, open- 

 ing of Eustachian tube ; •«»', frontal sin\is ; hh", 

 sphenoidal sinus ; c i, atlas vertebra ; v. ii, axis 

 vertebra. (After ^\'iedersheim.) 



ned about in different directions. 





FiG. 1210.— Parts of the Human ear (diagrammatic). C'cA. cochlea : E. Eustachian tuTie ; Ex. 

 outer opening of ear ; L. labyrinth ; M. tympanic membrane ; N. entrance of auditory nerve ; 

 Oj. O-i- O-i- the three auditory ossicles — stapes, incus, malleus. (After Headley ) 



Enclosed by its basal pnrt is the opening of the co:ternal auditory 

 'passage (Fig. 1210, Ex.). This, the length of which varies, leads 



