REPTILES 1387 



partly in the structure of the skin, which, in almost 

 every species, is covered with numerous scales: and 

 partly in the peculiar conformation of the ribs. The 

 edges of the scales form rough projections, which are 

 directed backward, so as to catch the surfaces of the 

 bodies to which they are applied, and to prevent any 

 retrograde motion. In some species, the integument 

 is formed into annular plates, reminding us of the 

 structures so prevalent among worms and myriapode 

 animals. Each scale is connected with a particular 

 set of muscular fibres, capable of raising or depress- 

 ing it, so that, in this way, it is converted into a kind 

 of toe; and thus the body rests upon the ground by 

 numerous fixed points of support. 



This support is further strengthened by the con- 

 nection of the ribs with the abdominal scuta, or the 

 scales on the under side of the body. The mode in 

 which the ribs become auxiliary instruments of pro- 

 gressive motion was first noticed by Sir Joseph Banks. 

 While he was watching the movements of a Coluber 

 of unusual size which was exhibited in London, and 

 was moving briskly along the carpet, he thought he 

 saw the ribs come forward in succession, like the feet 

 of a caterpillar. Sir Everard Home, to whom Sir 

 Joseph Banks pointed out this circumstance, verified 

 the fact by applying his hand below the serpent, and 

 he then distinctly felt the ends of the ribs moving 

 upon the palm, as the animal passed over it. The 

 mode in which the ribs are articulated with the 

 spine is peculiar, and has evidently been employed 

 with reference to this particular function of the ribs, 

 which here stand in place of the anterior and poste- 



