40 TUE HUMAN BODY. 



correspond pretty closely to one another; the pectoral 

 arch answers to the pelvic ; the humerus to the femur ; 

 the radius and ulna are represented by the tibia and 

 fibula ; five metacarpal bones correspond to fiye metu- 

 tarsal, and fourteen phalanges in the digits of the hand to 

 fourteen in the digits of the foot ; elbow and knee-joints, 

 and wrist and ankle are comparable. There is, however, 

 in the arm no separate bone at the elbow answering to the 

 patella at the knee ; but the ulna bears above a bony 

 process, 0, which is in early life a separate bone and 

 represents the patella. There are in the adult carpus 

 eight bones, in the tarsus but seven ; here again we find, 

 however, that originally the astragalus, Ta (Fig. 19), of 

 the tarsus consists of two bones. The elbow-joint bends 

 ventrally^ud the knee-joint dorsally. 



When we compare the limbs as a whole greater differ- 

 ences come to light, differences which are related to their 

 different uses. The arms, serving as prehensile organs, 

 have all their parts as movable as is consistent with the 

 requisite strength ; the lower limbs, having to carry all the 

 weight of the body, have their parts more firmly knit 

 together. Accordingly we find the shoulder girdle, C, 8 



Do the upper and lower limbs correspond in general plan of struc- 

 ture ? What in the lower limb answers to the pectoral girdle ? 

 What to tho humerus ? What bones to those of the forearm ? What 

 to the metacarpal ? Do the phalanges of the hand and foot agree in 

 number ? What joints in the leg answer to elbow and wrist ? 



What bone in the leg is not represented by a separate bone in the 

 arm of adults? What in the arm corresponds to this leg bone? Is it 

 ever a separate bone? Which has more bones, hand or foot? How 

 many bones are there in the tarsus in infancy? How many after 

 wards unite to form one? What is the bone formed by this union 

 named? How do elbow and knee joints differ as to the direction in 

 which they bend? 



Why are the arms made as movable as possible? Why ar tia 

 lower limb bones more firmly knit? 



