74 ELEMENTARY BIOLOGY. [CHAP. 



a. The distal tarsal series ; two in number in the 

 adult and imperfectly ossified ; viz. a larger 

 compressed post-axial element, giving articu- 

 lation to the second and third digits ; a smaller 

 nodular pre-axial cartilage (hallux tarsal\ lying 

 in the interspace between the heads of meta- 

 tarsalia i and 2 (it may be absent). 



/?. The central element (naviculare) ; triangular and 

 preaxial, interposed between the astragalus, and 

 hallux metatarsal. 



y. The calcar (pre-hallux) ; seen to be composed, 

 except in very old frogs, of three pieces, identical, 

 in their characters and relationships, with the 

 component parts of a digit. It is carried by /?. 

 In very young specimens a fourth segment may 

 be detected. 

 H. Myology; as illustrated in the hind limb. 



(For the following dissection it is desirable to have 

 a frog which has been lying some time in spirit.) 



Pin the animal down on its back, and remove the 

 skin from the hind limbs. 

 . i. General. 



In dissecting the muscles, separate them gently 

 from one another, tearing through the connective 

 tissue which unites them. 



a. Each is chiefly made up of a main mass, or belly. 



b. At both ends, in most cases, the belly is replaced 

 by dense shiny tissue forming a tendon. 



c. The tendons are fixed directly or indirectly to 

 some of the neighbouring bones, the less move- 

 able attachment is termed the origin of a given 

 muscle ; the more moveable its insertion. 



