410 



THE MECHANICAL FUNCTIONS. 



toe, (represented in Fig. 211), there are as many as 

 sixteen transverse slits, leading to the same number 

 of cavities, or sacs : these open forwards, and their 



external edge is serrated, 

 212 211 appearing like the teeth 



of a small-toothed comb. 

 A section of the foot, 

 showing these cavities, is 

 seen in Fig. 212. 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 ten- 

 dons of these muscles 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 

 on 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 cannot be supported by the feet, but must depend 

 altogether on the suspension derived from a suc- 

 cession of rapid and momentary adhesions. 



Although the Sauria are better formed for pro- 



Philosophical Transactions for 1816, p. 151, and 323. 



it'i 



