SKELETON OF LOWER LIMB. 



20: 



This process may attain a very great size, as e.g. in the 

 Ornithorhynchus and Echidna. 



In man alone does the external malleolus descend greatly 

 below the internal malleolus. The lower end of the fibula 

 may be very much enlarged, as in the Hippopotamus. - Its 

 lower end may develop a conical process, which, turning in- 

 wards, may fit into a depression 

 on the outer side of the articular 

 surface of the astragalus, as in 

 the Sloth. 



15. Inasmuch as the FOOT of 

 man is made up of the tarsus, 

 metatarsus, and phalanges, it 

 agrees with the same part in 

 Mammals and Batrachians. 



In Birds, however, the proxi- 

 mal part of the tarsus is an- 

 chylosed with, and in Reptiles 

 more or less firmly united with, 

 the tibia, so that the visible foot 

 of Birds corresponds but with 

 the greater portion and not the 

 whole of the foot of man. 



The foot, in one aspect, is less 

 constant than the hand, as ele- 

 ments of the leg (as in Balcena 

 and Bod) may be present while 

 there is no rudiment whatever 

 of the foot. 



1 6. In that the TARSUS of man 

 contains certain small and dis- 

 tinct bones, it agrees with the 

 same part in all Vertebrates 

 above Fishes, except Birds (in 

 which the tarsus coalesces with 



other portions of the skeleton), and except also certain 

 Tailed-Batrachians, in which the constituent parts of the 

 tarsus remain more or less permanently cartilaginous. 



The number of ossicles, or cartilages, may be as many as 

 nine, as in the Salamander ; or may be reduced to three, as in 

 Proteus, Bufo bifurcatus, and Lacerta agilisj or perhaps to 

 two, in Ophiodes striatus. 



We have seen that part of the carpus of man may be 

 represented by more elongated bones, as in the Crocodile. 



FIG. 173 ANTERIOR ASPECT OF 

 BONES OF RIGHT LEG OF Orui- 

 tliorkynchus paradoxns. 

 /, femur ; t, tibia ; f, fibula ; 



/, patella. 

 {From Flcnver's "Osteology.") 



