REPTILES 1393 



provided for effecting the adhesion of the feet to 

 the objects to which they are applied. It is somewhat 

 analogous to that employed in the case of the house- 

 fly, already mentioned. Each foot has five toes; 

 all, except the thumb, terminated by a sharp curved 

 claw. On the under surface of each toe there are 

 as many as sixteen transverse slits, leading to the 

 same number of cavities, or sacs; these open forward, 

 and their external edge is serrated, appearing like 

 the teeth of a small-toothed comb. All these parts, 

 together with the cavities, are covered or lined with 

 cuticle. Below them are large muscles which draw 

 down the claw; and from the tendons of these mus- 

 cles arise two sets of smaller muscles, situated so 

 as to be put upon the stretch, when the former are in 

 action. By the contractions of these muscles the 

 orifices of the cavities, or sacs to which they belong, 

 are opened, and the serrated edges applied accurately 

 to the surfaces with which the feet are in contact. 

 Sir Everard Home, in his account of this structure, 

 compares it to the sucking disk of the Remora. By 

 its means the animal is enabled to walk securely upon 

 the smoothest surfaces, even in opposition to the 

 tendency of gravity. It can run very quickly along 

 the walls or ceiling of a building, in situations where 

 it can not be supported by the feet, but must depend 

 altogether upon the suspension derived from a suc- 

 cession of rapid and momentary adhesions. 



Although the Sauria are better formed for pro- 

 gressive motion than any of the other orders of rep- 

 tiles, yet the greater shortness and oblique position 

 of their limbs, compared with those of mammiferous 



