80 STUDIES IN ADVANCED PHYSIOLOGY. 



PECTOEAL AND PELVIC GIEDLES AND THE EXTREMITIES. 



More or less firmly attached to this trunk are the two 

 girdles of the body, the pectoral girdle, supporting the arms, 

 and the pelvic girdle, for the attachment of the limbs. The 

 pectoral girdle consists on each side of two bones, the 



Fig. 26. RIGHT CLAVICLE, FROM ABOVE. 



Fig. 27. ANTERIOR VIEW OF RIGHT 

 SCAPULA. 



clavicle and the scapula. The clavicle articulates with the 

 manubrium of the breast bone and with the large acromion 

 process of the scapula. This serves to hold the shoulder 

 back in place. Animals that walk on their four limbs have 

 the clavicle reduced to a mere splint or thread of cartilage, 

 as it would be in their case undesirable to have the shoul- 

 ders pitched back. This reduction of the clavicle allows 

 the shoulders of these animals to drop under the body, a 

 position much better suited for supporting their weight. 



