SNAKES. 93 



SNAKES; OPHIDIA. 



The large and important order at which we now arrive, consists of reptiles which are 

 popularly known as Snakes, or more scientifically as Opiiidia, and to which all the true 

 serpents are to be referred. 



Almost every order is bordered, so to speak, with creatures so equally balanced between 

 the characteristics of the orders that precede and follow it, that they can be with difficulty 

 referred to their right position. Such, indeed, is the case with the Opiiidia, from which are 

 excluded, by the most recent systematic zoologists, the amphisbsenians and many other footless 

 reptiles, now classed among the lizards. The greater number of the Snakes are without any 

 vestige of limbs, but in one or two species, such as the pythons, the hinder pair of limbs 

 are represented by a pair of little horny spurs placed just at the base of the tail, and are 

 supported by tiny bones that are the undeveloped commencements of hinder limbs. Indeed, 

 several of the true lizards, the common blind-worm, for example, are not so well supplied with 

 limbs as these true Snakes. 



The movements of the serpent tribe are, in consequence, performed without the aid of 

 limbs, and are, as a general rule, achieved by means of the ribs and the large cross scales that 

 cover the lower surface. Each of these scales overlaps its successor, leaving a bold horny 

 ridge whenever it is partially erected by the action of the muscles. The reader will easily see 

 that a reptile so constructed can move with some rapidity by successively thrusting each scale 

 a little forward, hitching the projecting edge on any rough substance, and drawing itself for- 

 ward until it can repeat the process with the next scale. These movements are consequently 

 very quiet and gliding, and the creature is able to pursue its way under circumstances of con- 

 siderable difficulty. 



Oftentimes the Snake uses these scales in self-defence, offering a passive resistance to its 

 foe when it is incapable of acting on the offensive. Any one may easily try this experiment 

 by taking a common field Snake, letting it glide among the stubble or into the interstices 

 of rocky ground, and then trying to pull it out by the tail. He will find that even if the 

 reptile be only half concealed, it cannot be dragged backward without doing it considerable 

 damage, for on feeling the grasp, it erects all the scales and opposes their edges so effectually 

 to the pull that it mostly succeeds in gliding through from the hand that holds it. I 

 have often lost Snakes by allowing them to insinuate themselves into crevices, and have been 

 fain to let them escape rather than subject them to the pain, if not absolute damage, which 

 they must have suffered in being d ragged back by main force. 



The tongue of the Snake is long, black, and deeply forked at its extremity, and when at 

 rest is drawn into a sheath in the lower jaw. In these days it is perhaps hardly necessary to 

 state that the tongue is perfectly harmless, even in a poisonous serpent, and that the popular 

 idea of the "sting" is entirely erroneous. The Snakes all seem to employ the tongue largely 

 as a feeler, and may be seen to touch gently with the forked extremities the objects over which 

 they are about to crawl or which they desire to examine. The external organs of hearing are 

 absent. 



The vertebral column is most wonderfully formed, and is constructed with a special view 

 to the peculiar movements of the serpent tribe. Each vertebra is rather elongated, and is fur- 

 nished at one end with a ball and at the other with a corresponding socket, into which the ball 

 of the succeeding vertebra exactly fits, thus enabling the creature to writhe and twine in all 

 directions without danger of dislocating its spine. This ball-and-socket principle extends 

 even to the ribs, which are jointed to certain rounded projections of the vertebra? in a manner 

 almost identical with the articulation of the vertebra? upon each other, and as they are moved 

 by very powerful muscles, perform most important functions in the economy of the creature 

 to which they belong. 



Sometimes the Snakes advance by a series of undulations, either vertical or horizontal, 

 according to the species, and when they proceed through water, where the scales of the 



