File:Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct - for the use of schools and colleges (1870) (14779572201).jpg

Identifier: outlinesofcompar00agas (find matches)
Title: Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges
Year: 1870 (1870s)
Authors: Agassiz, Louis, 1807-1873 Gould, Augustus A. (Augustus Addison), 1805-1866 Wright, Thomas, 1809-1884
Subjects: Physiology, Comparative Zoology
Publisher: London : Bell & Daldy
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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tely under the power of thelever. The motions of the jaws of quadrupeds will be treatedof more in detail, when the anatomical structure of the rumi-nants, carnivora, and rodents is under special investigation. THE TRUNK. (§ 252. The most essential part of the skeleton is the verte-bral column, of which the skull may be considered an expan-sion, consisting, as it does, of three vertebra, the elements ofwhich have undergone great development, to encompass andenclose the three primary divisions of the brain. The osseousappears to follow the cerebro-spinal system, in the variousphases of its development, and may be regarded as a satellitemoving round the primary nervous centres. The vertebralcolumn occupies the middle line of the body, forming thecentral axis, which sustains all the other parts of the skeleton.It is composed in man of thirty-three vertebrae, arrangedinto those of the neck, back, loins, sacrum, and coccyx. (§ 253. A vertebra (fig. 105) is one of the segments of Fig. 105.
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the internal skeleton constituting this axis, and forming canals CEEYICAL YEETEBE^E. 127 for protecting the central trunks of the nervous and vascularsystems, and to which, likewise, sometimes, appendages areattached. A typical vertebra consists of a centre (centrum),and ten processes (apophyses). From the upper part ofthe centrum rise two neurapophyses, which form an archfor enclosing the spinal cord and brain. These are sur-mounted by a spine, called the neural spine. From the sidesof the centrum two transverse processes, or parapophyses, pro-ject, which sometimes carry ribs, or pleurapophyses. From theunder side of the centrum two processes descend to enclose thevascular trunks, in the same manner as the neurapophyses en-close the spinal cord, they are called h&mapophyses; fromthem descends a single haemal spine. The vertebral elements un-dergo various phases of development in the different classes,and in different regions of the spinal column of the same animal;it is therefore

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