A FROG 191 



into a close union with the breastbone and form with it a bony 

 and cartilaginous ring which almost completely encircles the 

 forward part of the trunk. 



Each half of the pectoral girdle supports one of the forelegs 

 and is composed of two portions, a dorsal and a ventral portion. 

 The former portion consists of two skeletal pieces of nearly equal 

 size, the suprascapula and the scapula, which lie respectively on 

 the dorsal and lateral sides of the body. The suprascapula — 

 the dorsal half — is a broad, thin plate which extends upward 

 over the spinal column. Its broad, free dorsal end is composed 

 of cartilage ; the remainder of it is bone. The scapula is an elon- 

 gated plate of bone which extends from the suprascapula to 

 the ventral side of the body. 



The ventral portion of the pectoral girdle consists of two 

 bony and three cartilaginous skeletal pieces. The two bones are 

 the coracoid and the clavicle, the former being the larger and the 

 more posterior in position, and extending from the scapula to the 

 midventral line. Joining them and the scapula is an irregular 

 cartilaginous mass in the hinder side of which is a depression, the 

 glenoid cavity, in which the humerus articulates. 



The breastbone, or sternum, lies in the medial area of the body, 

 between the ventral ends of the two pectoral girdles, and is made 

 up partly of bone and partly of cartilage. 



Remove the pectoral girdle with the foreleg from the body. In- 

 asmuch as it is not joined with the vertebral column it may be 

 removed by freeing it from the muscles in which it is embedded. 

 First locate accurately the delicate cartilaginous portions of 

 the sternum ; carefully locate also the delicate suprascapula on 

 each side of the body. Then insert the blade of a small scalpel 

 under the suprascapula on one side and free it from the muscles 

 which lie over it. Pass the scalpel down to the scapula and 

 then to the ventral portion of the pectoral girdle. Do the same 

 on the opposite side of the body, and finally remove the entire 

 girdle with the breastbone from the body. Disarticulate and re- 

 move the two forelegs and very carefully clean away the muscles. 



The Foreleg. The skeleton of the foreleg is composed of three 

 divisions, a proximal, a middle, and a distal division. 



