September 28, 1883.] 



SCIENCE. 



423 



of a box. It hinges upon the anterior border 

 of the meatus, and shuts backward. In some 

 cases the oporcuhim is about as long as the 

 whole skull is deep, and half as wide as long 

 — say, two inches long by an inch wide. On 

 raising such an ear-flap and turning it forward, 

 enormous external bonj- ear-parts, covered with 

 integument, are disphwed. Such expanse of 

 the outer ear results 

 from extension of oc- 

 cipital and squamosal 

 bones into a thin shell 

 bounding tlie meatus 

 externus above, be- 

 hind, and below. In 

 the best-marked cases 

 of the kind, especially 

 in Xyctala, the parts 

 are exaggerated iin- 

 symmetricall^on right 

 and left sides, and the 

 whole cranium is dis- 

 torted. This inllation 

 of tlie cranium does 

 not affect the inner 

 car- parts, or the es- 

 sential organ of hear- 

 ing. It should be add- 

 ed, in passing, that 

 the so-called ' ears ' 

 of various owls, as 

 the ' long-eared ' owl, 

 Asio otus, and • short- 

 eared' owl, Asio ac- 

 cipitriuus, are simply 

 tufts of feathers on top 

 of tlie head, over the 

 eyes ; these topknots 

 having nothing what- 

 ever to do with the 

 ears. Their proper 

 name is plumicorns. 



Aside from any 

 such irregularities, the 

 outer ear, or meatus 

 auditorius externus, is 

 a considerable, shal- 

 low, roundish depres- 

 sion, in the situation shown in fig. 1, where the 

 reference line 5 crosses it, and where the cross- 

 like object (stapes) marked st is seen l3'ing in it. 

 Its ordinary boundaries are, the enormous mal- 

 leus or quadrate bone, q, in front ; the ex- 

 panded rim of the squamosal, sq, above ; the 

 tympanic tuhig of the iwoccipital (a produc- 

 tion of the lateral condylar plate of the occipi- 

 tal, teo in fig. 2), beliind and below. A bone 

 unknown in human anatomy, the basi-temporal , 



Kio. 1. — Ripe chick's akull in proHlu,x3dinmctcr8. (.Afterl'ar- 

 ker.) pXf premaxilliiry ; fthi, uli-nat'al cartilaite; eii^ Bepto- 

 Daeal ; n, uai«al boue ; I, taclirymal ; pet perpendicular plate of 

 ethmoid ;»«. prcephenoidal region; a«, aliKphcnoid;/, frontal; 

 p, parietal ; «y, squatnosai ; .«o, superoccipital ; eo, exocclpital ; 

 oi\ occipital condyle; «/, the cross-iike object, the Htapea, 

 whose foot tits/enetitra ovutii ; c/, quadrate ; pg, pterygoid : «/;, 

 nuadraio-jugai ; J, juijai; pn, palatine; m*, maxillary; 3, optic 

 foramen ; <5, foramen ovttU, for inferior diviaionA of the tiftU 

 nerve. In tlie mandible : — f/,denlary; *«,8urangu!ar; «, angu- 

 lar ; art articular ; iap, internal angular process ; pap, posterior 

 angular procesa. 



which floors the Skull from ear to ear, un- 

 derlying the basi-occipital and basi-sphenoid, 

 also usually contributes to the inferior boundary 

 of the meatus. On removing the quadrate 

 (malleus), the general tympanic depression is 

 seen to be more or less dirccth' continuous with 

 the alisphenoid, and so to conduct into the 

 orbital cavit}' ; the boundary of the meatus 

 being best marked be- 

 hind and below bv the 

 expansive thin-edged 

 shell of the tympanic 

 wing of the exocclpi- 

 tal. To the brim in- 

 dicated is attached the 

 memlirana tympani ; 

 the ear - drum being 

 thus from the configu- 

 ration of the parts 

 quite superficial, in- 

 stead of being at the 

 bottom of a long cylin- 

 drical tube, as in man. 

 There is, in fact, in 

 birds, no • meatus au- 

 ditorius externus,' in 

 the sense of a special 

 bony tube; some slight 

 specks of ossification, 

 when an}-, about the 

 tj'mpanic membrane 

 itself, being all there 

 is of a tympanic bone 

 ( ' external auditor}' 

 process ' of human 

 anatomj') . 



Such shallowness, 

 openness, and super- 

 ficiality of the parts, 

 brings the cavit}' of 

 the tympanum or mid- 

 dle ear into full view 

 on removal of the tym- 

 panic meinbrane. On 

 looking into this cavi- 

 ty', as may readil}' be 

 done in clean, dry 

 skulls of any size, 

 many objects of interest may be studied without 

 further dissection. We observe in the first place 

 a large (inconstant) number of pueumatic fo- 

 ramina leading in various directions, conveying 

 air from the middle ear-i)assage into the air-cells 

 of l)ones of the skull, including the lower jaw. 

 The most special of these is a neat gristly or bon}' 

 air-tube into the lower mandible. Tlie mouth 

 of the eustachian tube is a large orifice at the 

 lower anterior part of the cavity. This tube, 



