274 GENERAL ORNITHOLOGY part ii 



There is ordinarily no external ear, in the sense of a fleshy 

 conch or auricle, though owls at least have a considerable flap which 

 overlies the auditory aperture. The place of an auricle is filled by 

 a set of peculiarly modified feathers surrounding and overlying the 

 ear -opening, called in ornithology the ear- coverts, or auriculars 

 (Fig. 25, ^5). The outer ear or meatus auditorius externus is a con- 

 siderable shallow roundish depression in the skull, at the extreme 

 lower lateral corner. Its ordinary boundaries are the movably 

 articulated quadrate bone in front, the expanded rim of the squa- 

 mosal above, the tympanic wing of the exoccipital behind and below ; 

 the termination of the basitemporal also usually contributing to the 

 under boundary. (See Fig. 71, at st ; 63, under I; Fig. 62, where 

 reference lines "bones of ear-cell" go.) On removing the quadrate 

 from the dry skull the general tympanic depression is seen to be 

 more or less continuous with the alisphenoid ; the boundary is best 

 marked behind and below by the broad thin sharp-edged shell of 

 the tympanic wing of the exoccipital. To the brim indicated is 

 attached the tympanum, or drum of the ear — that membrane being, 

 from the configuration of the parts, quite superficial, — not at the 

 bottom of a tube-like meatus, as in man. The membrane proper is 

 invested externally by modified common integument which readily 

 peels ofi'. Thus this wide shallow depression overlaid with feathers 

 or a slight flap is all there is to represent the " outer ear-passage." 

 The tympanic membrane sometimes develops slight ossification, 

 which then represents the " tympanic bone," or " external auditory 

 process " of human anatomy. Did not this membrane occlude the 

 way, the passage through the ear to the mouth would be pervious. 

 This passage is the modified persistence of the first visceral cleft or 

 " gill-slit " of the embryo. Just within the tympanic membrane is 

 the cavity of the tympanum or middle ear, which may be very exten- 

 sively exposed by merely removing the membrane. Looking into 

 this cavity, as may readily be done from the outside, in carefully 

 cleaned dry skulls, many objects of interest are presented ; among 

 them, a number of foramina — openings leading in various directions. 

 In the first place there are some (inconstant and not readily iden- 

 tified) holes, which are pneumatic openings, conveying air from the 

 middle ear-passage to the interior of bones of the skull and lower 

 jaw. Next is observed a large orifice in the lower anterior part of 

 the cavity, — the mouth of the Eustachian tube. This tube continues 

 the ear-passage to the mouth, and opens at the back of the hard 

 palate by a median orifice in common with its fellow. In clean 

 skulls of any size a bristle, or even a wooden toothpick, will pass 

 through the Eustachian tube, and appear upon the floor of the skull 

 in mid-line or nearly there, under the basisphenoid, over the basi- 

 temporal. The foregoing passages have not conducted us to the 



