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). 



(3. The central element (navicnlare) ; 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 ft. 

 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. 



I). 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. 



