CONCERNING SERPENTS. 



259 



tological research, and the expression is probably a figurative one, as 

 observed by Dr. Buckland. Serpents progress by the " foldings and 

 windings they make on the ground," and the stiff, movable scales 

 which cross the under portion of the body ; but the windings are side- 



ways, not vertical. 



Fig. 2. 



Aboma, ob Ringed Boa. 



The structure of the vertebrae is such, that upward and downward 

 undulations are greatly restricted, and many illustrations, showing 

 sharp vertical curves of the body, are exaggerations. Most persons 

 have seen snakes glide slowly and silently, without any contortion. 

 They seem to progress by some invisible power ; but, if permitted to 

 move over the bare hand, an experiment easily tried, a motion of the 

 scales will be perceived. These are elevated and depressed, and act 

 as levers, by which the animal is carried forward. Nor can a serpent 

 progress with facility on the ground, without the resistance afforded 

 by the scales. It is stated that it cannot pass over a plate of glass, or 

 other entirely smooth surface. We saw the experiment tried, by 



