OPHIDIAN A CR OB A TS. 213 



organization with due reverence, and witness it in activity — 

 as we admiringly observe the works of a watch in motion 

 — will forget to censure those who supply food to this piece 

 of animated mechanism, and even pardon a hungry little 

 snake for so expertly securing three birds at once. 



Think of 300 back-bones and 300 pairs of legs, all requiring 

 wholesome exercise. Some snakes have 300 pairs of ribs — 

 each pair capable of independent motion, and articulated with 

 that complex spine ; and each pair moving together, and 

 carrying along with them a foot in the shape of a broad 

 ventral scale. ' This scutum by its posterior edge lays hold 

 of the ground,' says Sir Everard Home, 'and becomes a 

 fixed point whence to set out anew.' 



The hold which the ventral scales have of the ground 

 obviously renders it easier for the reptiles to pass over a 

 rough than a smooth surface ; what are obstacles to other 

 creatures are facilities to them. But they appear to be 

 never at a loss. On a boarded room, or even a marble 

 floor, they will manage progression of some sort, — many by 

 the pressure of the tail to push themselves forward, and 

 others with an action that can be compared only with 

 swimming. With the same rapid, undulating motion as 

 swimming, the active snakes skim through the grass, or 

 over soft herbage, on which they seem to make no impres- 

 sion. Their swift sinuations are almost invisible to the 

 eye. You only know that a snake ivas there, and now has 

 vanished. The ' Rat ' snake of Ceylon {Ptyas mucosus) (see 

 frontispiece) and the ' Pilot ' snakes of America are among 

 the best known of these swift-flitting or gliding creatures. 

 Rats are fleet little quadrupeds, but their enemies, the 



