VESTIGIAL STRUCTURES, 99 
As the fibula in nearly all mammals is thin, slender, 
and almost vestigial, we have yet to inquire how it is 
that Pott’s fracture is peculiar to human beings. A 
comparison of the human malleoli with those of mammals 
shows that man differs from them in that the external or 
fibular malleolus descends much lower than the tibial 
malleolus: even in those mammals which so closely ap- 
proach man in anatomical characters as the gorilla, chim- 
panzee,orang,gibbon, and macaque, the malleoli are on the 
same level. In the accompanying sketches, fig. 50, the 
Fic. 50.—A, the malleoli of the Chimpanzee ; 
M, the malleoli of Man. 
malleoli of man and a chimpanzee are introduced for 
comparison. 
In 1886 Gegenbaur published the highly interesting 
observation that, in the human embryo at the fifth month 
of intra-uterine life, the tibial is more prominent than 
the fibular malleolus; at the seventh month they are 
equal; from this date onward the fibular exceeds in 
length the tibial malleolus. Thus at the fifth month the 
human malleoli present a condition common to the 
majority of mammals ; at the seventh month they corre- 
