Page:Popular Science Monthly Volume 4.djvu/272

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obvious to the touch, and this is true with those found in hot as well as in temperate climates, and adds greatly to their repulsiveness.

Fig. 1.
PSM V04 D272 Port natal python.jpg
Port Natal Rock-Snake, or Python.

Of serpents, their general form and structure are the same. Their bodies are rounded and elongated, and covered with a scaly skin. The vertebral column is continuous with the length of the body, and is divided into joints from 200 to 400 in number, but in the large pythons (Fig. 1), as stated by Dr. Carpenter, 422 vertebral joints have been counted. To about 360, or 6/7 of these, were attached pairs of movable ribs. A rattlesnake, with 194 vertebræ, had 168 pairs of ribs. The vertebrae of the serpent are united by a most perfect ball-and-socket joint, and the ribs are joined to the vertebrae in a similar manner. These, held and worked by complete muscular adjustment, give to several their wonderful flexibility, strength, and crushing power.

The well-known boa-constrictor, and the aboma, or ringed boa of South America (Fig. 2), are illustrations of this class of serpents, the term constrictor being given from their power to close upon and compress whatever is within their folds.

The structure of the backbone of a serpent has direct relation to its locomotion, for it is without limbs, and rudiments of pelvic bones are found only in the boas, pythons, and a few other species. But, where the type shades off into allied reptilian forms, the rudimental limbs are developed and prominent.

We read that the curse pronounced upon the serpent was, "upon thy belly thou shalt go," and the inference seems to be that, previous to that time, its mode of progression was not upon its belly. This would imply a great anatomical change in the structure of the creature at the time in question, a change which, so far as we are aware, is not proved by paleon-