On the archetype and homologies of the vertebrate skeleton / by Richard Owen.

  • Richard Owen
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: On the archetype and homologies of the vertebrate skeleton / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    ox TIIK VERTEBRATE 8KELETOX. two neurapophyses and the two parapophyses; but the terminal concave.* ' of the centrum are separately ossified. They coalesce with the intern • part of the centrum, which is sometimes completely ossified, but comm communicating aperture is left between the two terminal cones; many cases, the plates by which calcification attains the periphery . body leave interspaces permanently occupied by cartilage, formino- c in the dried vertebra, especially at tlieir under part, or giving a reti surface to the sides of the centrum. The expanded bases of the neu 1 par-apophyses usually soon become confluent with the bony centrum • i times first expanding so as wholly to inclose it, as, for example, in theil where the line of demarcation may always be seen at the border of th.l cular concavity, though it is quite obliterated at the centre, as a s 1 through that part demonstrates. 1 Muller correctly distinguishes a ‘central’ from a ‘peripheral’ (corticat|| or seat of the ossification of the vertebral bodies of fishes. The peri * ossification which takes its rise from the outer layer of the fibrous she f!' the notochord sometimes extends into broad plates beneath the anterioi tebras of the trunk, and tends to fix or anchylose a certain number of i3 when they are commonly represented by the partially distinct central * of the bodies, together with the neur- and par- and pleur-apophyses. jr The batracliia follow closely the stages above-cited in fishes; the cen ■ being arrested at the biconical stage in the perennibranchiates, but con^« into ball-and-socket vertebrae by the ossification of the interposed gelat* ball* and its adhesion, either to the fore-part of the centrum {Pipa, # ?na?iclra^, or the back part ^Ifana, ]3ufo^. The mode of ossification centrum varies somewhat in batracliia. Miillert describes annular .111 cations in the sheath of the notochord of the Puna temporaria and /?. OT lenta, which support, at first, the neurapophyses. Duges, apparentl if' fluenced by M. berres so-called ‘ law of centripetal development,’ desoJr two cartilaginous nuclei, side by side; but the more obvious and bette.^ termined development of the vertebrae of fishes gives no countenance t(|ip bilateral beginning of ossification of the centrum as a general law. Th. # distinct bony nucleus in the centrum observed by Duges w^as bilobedj. afterwards cubical; but excavated before and behind, as well as bene.# The ossification of the centrum is completed by an extension of bone the bases of the neurapophyses, which effect, also, the coalescence of i with the centrum. In Pelobates fusctis, and Pelobafes cultripes, Muller fW the entire centrum ossified from this source, w'ithout any independent p - *1 of ossification. £ Tlie vertebras of the tail of the larvae of the anourans are represente. | stinctly only in the aponeurotic stage. Even when the change to cart* takes place, the tendency to coalescence has begun to operate, and only “ long neurapophyses are established on each side: the ossification of t't' plate,s extends into the fibrous sheath of the remnant of the coccygeal r j / chord, and they coalesce when the perishable parts of the tadpole-tail h J been absorbed, and the fore- and hind-legs developed, constituting the 1 1 often hollow', and inferiorly grooved coccygeal bony style. j In saurians, birds and mammals, the notochord is inclosed by carti ■ ? before ossification begins; which cartilage is continuous with the cartil *: nous neurapophyses §. In birds, the tw'o histological processes, chondril * Dutrochet, Memoires pour servir d I’Histoire Nat. et Physiol, des Aniraaux, &c., ^ p. 302. 1837. t Neurologic der Myxinoiden, 1840, p. 69. J Recherches sur les Batraciens, 1835, 4to, p. 106. § Muller, Vergleicheiide Auatomie dcr Myxinoideii, Neurologic, 1840, p. 74.