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Show 284 ON THE STRUC'TURE OF THE VER'l'EBRA'l'E SKULl.;. "Between the sphenoid and occipital bon~s, between the sp h enm' d an d pe t 1. o us bones , betwe. e.n the panetals (the tern- T • pora l bo nes ar e ca way) and the ocCipital bone, dra'' a hue, a•n d you have 1narked off t~1e first. vertebr~. Draw another hne between the two sphenoids, or, In Man, In front of the pterygoid processes; laterally, through the fissura orbitalis in. front of the alm magnm; lastly, between the frontals and the par1etals, and vou have the second vertebra separated from the last. ,; 1. Now, take the ear vertebra of a fcetus of any Mammal or of a Man; place beside it an incompletely-developed dorsal vertebra, or the third cervical vertebra of a Crocodile, and compare the parts of which the two are composed-their forms, their contents, and the exits of the nerves. " Aecording to Albinus and all nnatomists, each vertebra of a footus consists of three separate pieces-the body and the two arches, which together form the spinous, transverse, and oblique processes. You have the sa~e in the occi1~ita~ b?ne, only more distinct and separate. The pars basttla:tts Is a corpus vertebrtl3 still more separated from the condyloid parts, which form the lateral regions; these are again separated from the pars occipitalis, which forms the spinous process. In fact, this part itself is often split again, like the spinous processes in spina b({ida. The occipital bone, therefore, is decomposable, according to the mode of its origin, into five pieces, since the lateral, or articular, and the spinous parts appear as independent developments; as is found also in actnal vertebrro, which consist of five pieces, and in the third cervical vertebra of the Crocodile. Finally, I need take no further pains to prove that the occipital foramen is the lower aperture of a vertebral canal; that the foramen lacerum is an inter-vertebral foramen, and the occipital protuberance is a spinous process; that, therefore, the occipital bone, in respect of form, as of funution (si?ce it encloses the cerebellum_, as a continuation of the spmal marrow), is in every sense a true vertebra, since the mere naming of these parts is enough to cause their recognition as such. "You will think I have forgotten the petrous bono. No! It seems not to belong to the vertebrre as such, but to be tho .. 'rHE THEORY OF TilE YICRTEBUATE SKULJ,, 285 sensory organ in which the vertebral-the auditory-nerve loses itself, and, therefore, to be an organ as completely separated from vertebral production as any other Yiscu \ or as the ball of the eye; the deception lies only in this, that it is the essence of this organ to be ossified, as it is that of the eye to be crystalline. "The mastoid process is, in animals, and also in tho human footus, a proper bone, in which the styloid procos'l lies. It is plainly inserted into the first vertebra, but it receives its si()'ni- :fication from the tongue. 0 '' 2. Having entered so fully into the discussion of the first cephalic vertebra, I might, except for clearness' sake, spare you any delay over the second. But I will also demonstrate in this how completely the brain-case is formed according to the idea of a vertebra, and bas even been partially produced as such. "In every skull of a fcetus you may find the altl3 orbitales of the sphenoid separate from it. They belong to the third vertebra. But, in the half-developed frotns, the great wings and the pterygoid processes are also separate from the body of the sphenoid. The last-mentioned processes are foreign to the sphenoid, and only coalesced with it; they belong to quite another formation, and very probably have the same signification as the os 01noideum of the Bird's head, as Cuvier bas already indicated. I shall return to them. "There remain, therefore, for the posterior sphenoid, or the jaw vertebra, three portions of bone-the body and the great wings, or the lateral and oblique processes of the vertebra. ~rhe spinous processes are formed by the two parietals, which, in many animals, coalesce so as to leave no suture, but are yet originally t-wo. It is to be remarked that, in the Sheep, this vertebra is closed by the bones in question, without the intermediation of the temporal, which also doos not belong to the vertebral group. ~rhe same occurs in the Chelonian, the Crocodile, &c. "3. Whoso has recognised the second vertebra, as such, need only look at the third, especially in Ruminants, to discover quite the same structure. The anterior sphenoid with the alte orbitales represents the body, together with the lateral pro- |
