1384 THE STORY OF THE UNIVERSE 



brated skeleton can be reduced ; for it consists merely 

 of a lengthened spinal column, with a head but little 

 develpped, and a series of ribs; but apparently desti- 

 tute of limbs, and of the bones which usually connect 

 those limbs with the trunk. In the conformation of 

 the skull and bones of the face, they present strong 

 analogies with Batrachian reptiles, and also with 

 fishes, one tribe of which, namely, the apodous 

 or anguilliform fishes, they greatly resemble by the 

 length and flexibility of the spine. These peculiari- 

 ties of conformation may be in a great measure traced 

 to the mode of life for which they are destined. The 

 food assigned to them is living prey, which they must 

 attack and vanquish before they can convert it into 

 nourishment. The usual mode in which the boa 

 seizes and destroys its victims is by coiling the hinder 

 part of its body round the trunk or branch of a tree, 

 keeping the head and anterior half of the body dis- 

 engaged; and then, by a sudden spring, fasten upon 

 the defenceless object of its attack, and twining round 

 its body so as to compress its chest and put a stop to 

 its respiration. Venomous serpents, on the other 

 hand, coil themselves into the smallest possible 

 space, and suddenly darting upon the unsuspecting 

 or fascinated straggler, inflict the quickly fatal 

 wound.* 



It is evident, from these considerations, that, in the 

 absence of all external instruments of prehension 



* Their prey is swallowed entire ; and therefore, as we shall 

 afterward find, the bones of the jaws and face are formed to 

 admit of great expansion, and of great freedom of motion upon 

 one another. 



