180 MANUAL OF ANIMAL BIOLOGY 



of a number of bones and cartilaginous elements ; the principal 

 bones being the scapula, clavicle, and coracoid. The scapula 

 and coracoid on each side form a cavity, the glenoid fossa, into 

 which the proximal end of the humerus of the fore limb fits. (W. 

 f. 102, A.) 



The pelvic girdle, which forms the support and attachment of 

 the hind limbs, consists of a right and left half, each formed from 

 three bones, the ilium, ischium, and pubis, the first being the 

 largest. The ilium in the Frog connects anteriorly with the trans- 

 verse process of the ninth vertebra, continues posteriorly nearly 

 parallel with the median urostyle at the posterior end of the verte- 

 bral column, and, finally, connects with the ischium and the pubis. 

 The ischium and pubis together with the posterior end of the ilium, 

 form a common cavity, the acetabulum, into which the proximal 

 end of the femur of the hind limb fits. (W. f. 102, B.) 



Each fore limb consists, first, of a large bone, the humerus 

 which, as mentioned above, articulates at its proximal end with 

 the glenoid fossa of the pectoral girdle. The distal end of the 

 humerus articulates with the radio-ulna. This is a single fused 

 bone in the Frog, but in many of the Vertebrates it consists of two 

 separate bones, the radius and ulna. In the Frog there are six 

 wrist bones (carpals), three of which articulate with the radio- 

 ulna, and three of which articulate with the bones of the hand. 

 Each of the five digits of the hand begins proximally with a meta- 

 carpal bone. In digit I, there is no other bone. In digits II and 

 III, the metacarpals are followed by two phalanges, and in digits 

 IV and V, the metacarpals are each followed by three phalanges ; 

 thus making a total of five metacarpals and ten phalanges in the 

 hand of the Frog. (W. f. 103.) 



The hind limb of the Frog and of Vertebrates in general has the 

 same arrangement of parts as the fore limb. There is, first, a 

 large femur which is homologous with the humerus in the fore 

 limb. It articulates proximally, as mentioned above, with the 

 acetabulum of the pelvic girdle. The distal end of the femur artic- 

 ulates with the tibio-fibula. This is a single fused bone in the 

 Frog, but in many of the Vertebrates it consists of two separate 

 bones, the tibia and fibula. It is homologous with the radio- 

 ulna of the fore limb. The ankle bones (tarsals) of the Frog are 

 atypical. Each of the five digits of the foot begins proximally with 

 a metatarsal bone. In digits I and II, there are two phalanges 



