Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . to it by ligaments. The land salamanders havea rounded tail, but the aquatic species, or Tritons,have it compressed vertically; thus retainingthe fish-like form of the tadpole, and the sameradiated disposition of the muscles. human conformation in its organs of progressive motion. Thisarises from the exertions which it makes in swimming beingsimilar to those of man in walking, in as far as they both resultfrom the strong action of the extensors of the feet. Hence wefind a distinct calf in t
Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . to it by ligaments. The land salamanders havea rounded tail, but the aquatic species, or Tritons,have it compressed vertically; thus retainingthe fish-like form of the tadpole, and the sameradiated disposition of the muscles. human conformation in its organs of progressive motion. Thisarises from the exertions which it makes in swimming beingsimilar to those of man in walking, in as far as they both resultfrom the strong action of the extensors of the feet. Hence wefind a distinct calf in the legs of both, produced by the swellingof similar muscles. The muscles of the thigh present, also, manyanalogies with those of man ; particularly in the presence of thelong muscle calid the sartorius, the use of which is to turn thefoot outwards, both in stepping and in swimming. SERPENTS. 447 <^ 3. Ophidia. In the class of serpents we see exemplified thegreatest possible state of simplicity to which avertebrated skeleton can be reduced; for, as may be seen in Fig. 201, which shows the skeleton. of a viper, it consists merely of a lengthenedspinal column, with a head but little developed,and a series of ribs ; but apparently destitute oflimbs, and of the bones which usually connectthose limbs with the trunk ; there being neithersternum, nor scapula, nor pelvis.* In the con- * Professor Mayer has, however, traced obscure rudiments ofpelvic bones in the Anguis fragilis, the Anguis ventralis, andthe Typhlops crocotatus, and is of opinion that they existmuch more generally in this order of reptiles, than has beencommonly imagined. Some serpents, as the Boa, Python, Tor-tryx and Eryx, have claws, which may be considered as rudi-ments of feet, visible externally. In others, as the Anguis, Typh-lops, and Amphisbcena, they exist concealed under the skin. 48 THE MECHANICAL FUNCTIONS. formation of the skull and bones of the face,they present strong analogies with batrachianreptiles,
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