. Animal physiology. Physiology, Comparative; Physiology, Comparative. STRUCTURE OF THE VERTEBRAL COLUMN. 461. the skeleton, only by ligaments and muscles ; but in Birds it is connected with the temporal bone on each side, by a set of bony pieces jointed together, like links in a chain. 626. The most important part of the Trunk, and even of the whole skeleton,—that which serves to sustain the rest, and which varies the least in the different classes of Ver- tebrated animals,—is the spinal or vertebral column. The general conformation of this has been already described (§. 64). In Man it consis
. Animal physiology. Physiology, Comparative; Physiology, Comparative. STRUCTURE OF THE VERTEBRAL COLUMN. 461. the skeleton, only by ligaments and muscles ; but in Birds it is connected with the temporal bone on each side, by a set of bony pieces jointed together, like links in a chain. 626. The most important part of the Trunk, and even of the whole skeleton,—that which serves to sustain the rest, and which varies the least in the different classes of Ver- tebrated animals,—is the spinal or vertebral column. The general conformation of this has been already described (§. 64). In Man it consists of 33 ver- tebrae, which are arranged into five divisions ;—I. The cervical vertebras, c, or vertebras of the neck, of which there are 7; H« The dorsal vertebras, d, or vertebras of the back, of which there are 12 ;—III. The lumbar vertebras, /, or vertebras of the loins, of which there are 5 ;—IV. The sacral vertebras, s, of which also there are 5 ;—and V. The coccygeal ver- tebras, co, of which there are 4. All these vertebras are separate at the time of birth ; but the 5 sacral ver- tebras are soon afterwards united into one piece, Pl^ 214 forming the bone which is termed the sacrum ; and Vertebral the coccygeal vertebras are also commonly united into one piece, the coccyx, which is not unfrequently united in old age to the sacrum. In old persons, too, it is not uncommon for the lumbar vertebras to be united together, by bony matter deposited in their cartilages and ligaments. 627. The dorsal vertebras are distinguished from the cervical and lumbar, as being those to which the ribs are attached. It is remarkable that the number of the cervical vertebras should be the same in all the Mammalia; the long-necked Giraffe having only 7; and the Whale, whose head seems to be joined to its body without the intervention of any neck, also having 7 cer- vical vertebras, although they are almost as thin as a sheet of paper. It is owing to the small number of joints in i
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