An elementary course of practical zoology / by T. Jeffery Parker and W.N. Parker.

  • Thomas Jeffery Parker
Date:
1908
Catalogue details

Licence: In copyright

Credit: An elementary course of practical zoology / by T. Jeffery Parker and W.N. Parker. Source: Wellcome Collection.

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    3. The shoulder-girdle or pectoral arch, an inverted arch of bone and cartilage nearly encircling the anterior part of the trunk and giving attachment to— 4. The bones of the fore-limbs. 5. The hip-girdle or pelvic arch, an apparatus shaped somewhat like a bird’s “merrythought”: it is attached in front to the ninth vertebra and behind gives attachment to— 6. The bones of the hind-limbs. The Vertebral Column.—The essential structure of a vertebra may be best studied by examining any of the nine from the second to the seventh : the first, eighth, and ninth present certain peculiarities, and so may be left till last. . The whole vertebra (Fig 8, B) has something the form of a signet-ring with its sides produced into two outstanding projections. The part comparable to the stone of the ring is ventral in position, and is called the body or centrum (cn), the form of which is procoelous, i.e., its anterior face is concave, its posterior face convex, and both faces are covered with a thin layer of cartilage, d he part corre- sponding with the circle of the ring is the neural arch (pd, Im) : it arches over the spinal cord and is produced in the middle line above into a blunt projection, the neura\ spine (n. sp). From the arch is given off, on either side, the large outstanding projection already referred to, the transverse process (tr. pr), which is tipped with cartilage in the second, third, and fourth vertebras. The neural arch gives off from its anterior face, just above the origin of the transverse processes, a pair of small shelf- like projections, the articular processes or zygapophyses (a. zyg). Each has its upper surface flat and smooth, and covered with a thin layer-of cartilage. A similar pair of processes spring (rom the posterior face of the arch, but have the smooth, cartilage-covered surface or facet looking downwrards.
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