354 LEAVES FROM THE 



on the ground, without external feet or wmgs, seems hardly 



less hopeless. Those who have seen a snake rapidly 



vanish among the herbage, or climb the side of a dry 



ditch and escape among the thorns of the hedge, will 



allow that the task has been most efficiently performed. 



And how ? 



There is a great deal of geometrical neatness and nicety in the 

 sinuous motion of snakes and other serpents, (says good Mr. 

 Derham, canon of Windsor, and rector of Upminster, in Essex) ; 

 for the assisting in which action, the annidar scales under their 

 body are very remarkable, lying cross the belly, contraiy to Aihat 

 those in the back and the rest of the body do : also, as the edges 

 of the foremost scales lie over the edges of their following scales ; 

 so as that when each scale is drawn back, or set a little upright by 

 its muscle, the outer edge thereof (or foot, it may be called,) is 

 raised also a little from the body, to lay hold on the earth, and so 

 promote and facilitate the serpent's motion. This is what may be 

 easily seen in the slough of the belly of the serpent kind. But 

 there is another admirable piece of mechanism, that my antipathy 

 to those animals hath prevented my piying into ; and that is, that 

 every scale hath a distinct muscle, one end of which is tacked to 

 the middle of its scale ; the other, to the u^iper edge of its fol- 

 lowing scale. This, Dr. Tyson foimd in the rattle-snake, and I 

 doubt not is in the whole tribe. 



Certainly ; and Tyson and others, who either had not 

 the Rev. W. Derham's antipathy or conquered it, did 

 not stop at externals, but went a little deeper into the 

 matter. 



Blasius remarks that the knots of the vertebrse of the 

 viper are shorter towards the head, and hence that reptile 

 can easily bend itself both backwards and sideways. 

 Tyson observes, in his Anatomy of the Rattlesnake, 

 when treating of the vertebrae and the other curious 

 articulations, that the round ball in the lower part of the 

 upper vertebrse enters a socket of the upper part of the 

 lower vertebras, ' like as the head of the os femoris doth 

 the acetabulum of the os ischii, — by which contrivance, 

 as, also the articulation with one another, they have that 

 free motion of winding their bodies any way.' 



