134 UPPER EXTREMITIES AND 



titude of the body, would pass far behind the hip : thus the 

 upper limbs are thrown outwards and backwards, and have 

 a free range in their principal motions, which are in the an- 

 terior direction. The glenoid cavities look outwards. The 

 arms are widely separated above, and they diverge towards 

 their opposite ends ; the lower limbs, on the contrary, 

 converge from above downwards. In true quadrupeds, 

 the clavicles are suppressed * ; the shoulder-blades brought 

 forwards on the chest, and approximated to each other ; 

 and the glenoid cavities are directed downwards. Conse- 

 quently the anterior or pectoral members fall perpendicu- 

 larly under the front of the chest, and come still nearer to- 

 gether below than above. 



The deep cup of the os innominatum, and the powerful 

 orbicular ligament of the hip, are strongly contrasted with 

 the shallow glenoid cavity and weak capsule of the shoulder: 

 the difference between the broad articular surfaces and 

 very powerful ligaments of the knee, and the strong joint of 

 the ankle on one side, and the articulations of the elbow and 

 wrist on the other, is equally striking. 



The leg and fore-arm resemble each other less than the 

 thigh and arm : in the fore-arm, the parts are arranged fa- 

 vourably to mobility 5 in the leg, the object is to procure a 

 firm and solid support, which can transport the centre of 

 gravity with ease and safety from one point to another. Of 

 the two bones of the fore-arm, which are nearly equal in 



• It is stated, in the Physiological Lectures^ p. 123, that " no animal, ex- 

 cept the monkey, has a clavicle like that of man," Certainly none, without 

 excepting even the monkey, have either clavicles, or any other bones, exactly 

 resembling the human in all points; but man), even of the more common 

 kinds, have clavicles equal to those of man in relative size and length as v/eW 

 as in office. As the use of this bone is to maintain the shoulder at its proper 

 distance from the front of the trunk, and to prevent the scapula in particular 

 from coming forwards on the chest, it exists in all cases, where the pectoral 

 members are employed, either principally, or in great part, in executing pur- 

 poses foreign to support, such as holding objects, climbing, flying, digging, rak- 

 ing the ground. It will be sufficient to mention that the lemurs and bats, the 

 squirrel, beaver, rat, porcupine, mole, ant-eater, hedge-hog, shrew, and sloth, 

 possess perfect clavicles. 



