608 KEPT I LI A. 



General notes on snakes. - - Snakes, especially when 

 poisonous, are often brightly coloured. The scales on the 

 head form large plates, and those on the ventral surface are 

 transverse shields. In many cases there are odoriferous 

 glands near the cloacal aperture. 



The muscular system is very highly developed, and the 

 limbless serpent, Owen says, " can outclimb the monkey, 

 outswim the fish, outleap the zebra, outwrestle the athlete, 

 and crush the tiger." 



The vertebrae are very numerous, some pythons having 

 four hundred ; they are procoelous, and are distinguishable 

 only into a pre-caudal and caudal series. 



All the pre-caudal vertebrae except the first the atlas 



Tl 



FIG. 298. Snake's head. After Nuhn. 



dv., Poison fangs ; b., sheath of fang ; /., tongue ; rl., muscles of 



tongue. 



have associated ribs, which are movably articulated, and 

 used as limbs in locomotion. In the caudal region the 

 transverse processes, which are elsewhere very small, take 

 the place of ribs. 



The serpent "literally rows on the earth, with every 

 scale for an oar; it bites the dust with the ridges of its 

 body." On a perfectly smooth surface it can make no 

 headway, but in normal conditions the edges of the 

 anterior ventral scales are fixed against the roughnesses of 

 the ground, the ribs are drawn together first on one side, 

 then on another, the body is thus wriggled forward to the 

 place of attachment, the front part shoots out as the hind 

 part fixes itself, an anterior attachment is again effected, 



