OCTOUKR "ill, ISSO. 



SC/ENCE. 



553 



gold bone (lig. 1 . pg) . and so with the palate- 

 bone (lig. 1, pa) and superior maxillary {m^-), 

 4, 5. The head of the bone normally articulates 

 both with the s(iuamosal (tig. 1, sq) and with 

 the pro-otic (fig. 4, j)0, here seen inside the 

 cranial cavity). A long spur of the quad- 

 rate, its orbital process, projects freely into 

 the orliital cavity, as shown in fig. 1, where 

 the still cartilaginous tip of the orbital process 

 reaches to the round white hole marked l' 

 {optic foramen). Now, the osseous articula- 

 tions and muscular tractions are such, that, 

 when the month is opened, the malleus rocks 

 forward upon its squamosa-petrosal articula- 

 tion (4, .i, of aliove enumeration), and pushes 

 upon tlie zygomatic and plerygo-palatal bars, 

 causing the upper mandi- 

 ble to rise as the lower jaw 

 is depressed ; the upper jaw 

 hinging ni)Oii elasticity of, 

 or a joint at, the bones of 

 the forehead. Thus the 

 malleus - quadrate is here 

 seen in its proper relation 

 to the jaw-parts as nothing 

 at all of an ossiculum audi- 

 tus, except in so far as it 

 hinges upon jjarts of the 

 temporal lione, and helps 

 to support the ear-drum. 

 It has no direct connection 

 wiiatever with the rest of 

 the ossicles. 



It will be best to take the 

 stapes next. Fig. 3 shows 

 the mature stapes of the 

 domestic fowl , enlarged 

 about four times, and indi- 

 cates its several elements 

 which have received spe- 

 cial names. It is practically the same bone 

 so named in man, but includes incudial as well 

 as some other elements. In form it is not at 

 all stirrup-like, being trumpet-shaped, with a 

 slender cylindrical shaft, expanded oval foot, 

 and a crossbar and other pieces at the distal 

 end. It is therefore oflener called the colu- 

 mella auris. or sounding-post of the ear. In 

 skulls prepared with sutlicient care, the stapes 

 may be seen in situ, as in fig. 1, st, — an e.x- 

 tremel}' delicate rod, ste|)ped into the fenestra 

 ovalis by its foot, the other end protruding into 

 the tympanum, and bearing the additional ham- 

 mer-like or claw-like elements. A stapes I 

 have just picked out of an eagle's ear is a 

 fourth of an inch long, with a stem as line as 

 a thread of sewing-silk, but a stout foot, and, 

 at the tympanic extremity, a still finer hair-like 



[G. ;i. — Mature eliipt's 

 of fowl, about X 4. 

 (After Tarkur.) at, 

 its foot, titting/f'nc^- 

 tra ovalin; mut, main 

 shaft, or medio-stjtpe- 

 dial clement; «A^ 

 supra-stapedial ; eat, 

 extra- stapedial; iMt, 

 in f ra-»tapediai, its 

 end representing a 

 rudimentary s/ylo- 

 hyal; /, a fenestra in 

 tlic extra- stjipedial. 

 (See Hi, in ailli, til!. 1, 

 and its embryonic for- 

 mation, tig. 2.) 



l)i-oeess half as long as the main stem, from 

 which it stands out at right angles : while there 

 appears to have been another similar claw, 

 which has broken off from such a cross-like 

 object as St in fig. 1. 



Embrvological study is required to demon- 

 strate tiie stapes as the proximal element of 

 the hyoidean apparatus, quite as the malleus is 

 of the mandibular arch. Reference to fig. 2 

 should make this clear. Ileie the malleus, q, 

 extends from teo, the tympanic wing of the 

 exoccipital, to ar, the articular element of mk, 

 the meckelian rod whence q has been seg- 

 mented off, leaving the ' temporo-maxillaiT 

 aiticulation ' between q and ar. This chain of 

 bones, including others to be developed about 

 and beyond the stump of mk, is the lower jaw, 

 or mandibular arch. Now, quite a similar ar- 

 rangement is shown in the chain of bones in 

 the tongue or hyoidean arch. From teo stands 

 off a rod of bone, w st. the medio-stapedial 

 element, or main shaft of the stapes, to be seg- 

 mented awa3-from teo. the place of this segmen- 

 tation to become the fenestra ovalis. The 

 medio-stapedial rod expands at its end ; the 

 ujiper part of the expansion, never separating 

 from the rest, is the supra-stapedial element= 

 mammalian incus, s st in figs. 2, 3. An iufra- 

 stapedial element, just forming in fig. 2, ist, 

 completed in fig. 3, ist, connects with the piece 

 marked st h in fig. 2. This st h is the stylo- 

 hyal= human ' styloid process of the temporal,' 

 which connects in man by the ' stylo-hyoid liga- 

 ment,' with the ' lesser coruu of the liyoid bone,' 

 which is the cerato-hyal, c hy. In bii-ds, the 

 distal parts of the hyoid arch (composed of the 

 numerous pieces lettered in fig. 2, but which 

 need not longer detain us) become entirely sep- 

 arated from tlie proximal, the tongue-bones 

 being quite otherwise affixed to the skull ; while 

 the proximal parts of the same arch are shut 

 up in the tympanic cavity, where they extend 

 fiom the membruna tympani to the fenestra 

 ovalis, constitute all there is of ossicula audi- 

 tus, and consist of the stapes itself (including 

 the several elements specified) . 



So, therefore, avian malleus or quadrate- 

 bone = human malleus as proximal element of 

 mandibular arch, retaining articular connection 

 with its own arch, but not acquiring character 

 or connections of a human ossiculum auditus. 



So, therefore, avian stapes or columella = 

 human stapes -|- incus, as proximal elements of 

 hyoidean arch, not retaining connection with its 

 own arch, but acquiring ch,aracters and con- 

 nections of ossicula auditus. 



These are the reasons why a bird's lower jaw 

 does not articulate directlj- with the squamosal, 



