THE FROG 123 



a proximal and a distal row. The hand is made up of five digits, 

 of which the first digit, or thumb, is very small and rudimentary. 

 Each of the other four digits is composed of two parts,— the meta- 

 carpus, the long proximal bone which articulates with the carpus, 

 and the phalanges, two or three small bones which form the finger. 

 The thumb contains a metacarpus alone. 



Exercise 29. Draw the foreleg in outline, showing accurately all the 

 bones and cartilages ; label them all carefully. 



The Posterior Appendages. These consist of the hind legs and 

 of the pelvic girdle which joins them with the trunk. 



The pelvic girdle, like the pectoral, is composed of a right and a 

 left half which meet ventrally and form an arch. The dorsal ends of 

 the arch articulate with the last vertebra of the spinal column ; and 

 at its ventral end, on each side, is the acetabulum, the articular sur- 

 face of the hind leg. Extending backward from the last vertebra 

 between the two sides of the pelvic girdle is the long bone called 

 the urostyle, which forms the hinder part of the spinal column. 



Each half of the pelvic girdle is composed of two portions, a 

 dorsal and lateral portion and a ventral portion. The former con- 

 sists of the long, slightly arched ilium, which forms the side of the 

 arch and articulates dorsally with the last vertebra. The ven- 

 tral portion is disk-shaped and is composed of the ventral end 

 of the ilium, a small triangular bone called the ischium, and a 

 small triangular cartilage called the pubis ; the pubis is anterior 

 to the ischium in position. The ilium, ischium, and pubis cor- 

 respond to the scapula, coracoid, and procoracoid, respectively, in 

 the pectoral girdle. 



Carefully strip the muscles from the pelvic girdle, disarticulate it 

 from the vertebral column, and remove it and the hind legs from 

 the body. Disarticulate the legs and thoroughly clean the pelvis. 



Exercise 30. Draw two views of the pelvis on a scale of 2, one of 

 the lateral aspect and one of the dorsal aspect. 



The Hind Leg. The skeleton of this leg closely corresponds to 

 that of the foreleg. It is made up of three divisions,— a proximal, 

 a middle, and a distal division. 



