28 THE FROG 



how do they differ? Make a sketch of the skeleton of the frog from 

 the dorsal view, showing as many of the bones as possible. The bones 

 of the skeleton may be classified as follows: 



I. The Axial Skeleton: the Skull and Vertebral Column. 



The skull includes the cranium, or brain case, and the bones of 

 the face and jaws. 



The vertebral column is composed of nine vertebrae. Posterior 

 to the last vertebra is the elongated urostyle. The first or 

 most anterior vertebra is the atlas and has no transverse 

 processes which are found on the other vertebrae. The ninth 

 or most posterior vertebra is the sacrum, to which the hip 

 girdle is attached. 



II. The Appendicular Skeleton: Girdles and Appendages. 



The shoulder girdle includes the sternum, or breastbone; the 

 clavicle, or collar bone; the coracoid, a large bone just pos- 

 terior to the clavicle; and the scapula and suprascapula, 

 which together constitute the shoulder blade. The hip girdle, 

 which is also called pelvic girdle and innominate bone, is 

 represented in the frog by a V-shaped bone formed by the 

 fusion of three paired bones, the ilium, the ischium, and the 

 pubis. The hip girdle is attached to the sacrum by the elon- 

 gated ilia which are seen parallel to the urostyle. 



The fore and hind limbs are articulated. with the shoulder and 

 hip girdles respectively. The identity of the fundamental 

 plan in each pair of limbs is shown by the following tabula- 

 tion in which the bones are listed in order from the proximal 

 to the distal end of the leg, that is, beginning with the bone 

 which is articulated with the girdle. 



BONES OF THE FORE LEG BONES OF THE HIND LEG 



Humerus (upper arm). Femur (thigh). 



Radio-ulna (forearm). Tibio-fibula (shin). 



Carpals (wrist), Tarsals (ankle), two long bones and 



six small bones. several small ones. 



Metacarpals (hand). Metatarsals (foot). 



Phalanges (fingers). Phalanges (toes). 



Exercise 24. — Joints. 



(b) Remove the muscles from the hip joint, or place where the 

 femur is articulated with the hip girdle. The joint is not at once 

 exposed as it is covered by a thin, tough membrane known as the 

 capsular ligament. This ligament attaches the femur to the hip girdle 



