35 



CHAPTER II. 



OPHIDIAN REPTILES, OR TRUE SNAKES. 



Reptiles are, as has been said in the preceding chapter, verte- 

 brated animals, breathing by lungs, having red and cold blood — ■ 

 that is to say, not producing sufficient heat to render their tem- 

 perature superior to that of the atmosphere ; destitute of hairs, 

 of feathers, of mammary glands, and having bodies covered with 

 scales. 



Snakes, properly so called, have the tympanic bone, or pedicle 

 of the lower jaw, movable, and nearly always suspended to another 

 bone analogous to the mastoid bone, which is attached to the cra- 

 nium by muscles and ligaments, a conformation which gives to these 

 animals the vast power of distension they possess. Their trachea 

 is long, their hearts placed far back, and the greater number have 

 one very long lung and vestiges of a second. They are divided 

 into non-venomous and venomous; and the latter are sub-divided 

 into venomous with maxillary teeth, and venomous with isolated 

 fangs. 



The Snakes prey almost exclusively on animals of their own 

 killing ; the more typical species attacking such as are frequently 

 larger than themselves, and the maxillary apparatus is, as we 

 have seen, modified so as to permit of the requisite distension. 

 According to Professor Owen's clear and t intelligible description, 

 the two superior maxillary bones have their anterior extremities 

 joined by an elastic and yielding fibrous tissue with the small and 

 single intermaxillary bone ; the lower maxillary rami are similarly 

 connected. The opposite extremity of each ramus is articulated to 

 a long and movable vertical pedicle formed by the tympanic bone, 

 which is itself attached to the extremity of a horizontal pedicle 

 formed by the mastoid bone, so connected as to allow of a certain 

 yielding movement upon the cranium. The other bones have 

 similar loose movable articulations, which concur in yielding to 

 the pressure of large bodies with which the teeth have grappled. 



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