100 EVOLUTION AND DISEASE. 
spond to the simian type, and subsequently assume the 
relation normal only in man. This extra length of the 
fibular malleolus gives great firmness to the ankle-joint, 
and has probably been acquired concurrently with the 
assumption of the erect posture. It is to this extra 
length of the outer malleolus, associated with the slender- 
ness of the fibula, that the frequency of Pott’s fracture 
may be largely attributed; the long fibular malleolus 
affording good leverage when the foot is violently and 
suddenly twisted laterally, the force applied to the long 
distal end causes the fibula to snap at some point in its 
lower fourth. 
This inquiry, when pushed further, leads to other 
points of interest. The foot of an orang, instead of 
forming a right angle with the leg, as in man, has its 
inner border drawn upwards in such a manner that the 
sole of the foot looks inwards, and the back, or dorsum, 
of the foot looks outwards. This position of the foot is 
associated with a peculiar disposition of the articular 
surfaces of the astragalus, or ankle-bone. In the human 
embryo, up to the seventh month, the foot has a similar 
position, and the articular surfaces are disposed as in the 
orang; after the seventh month the foot gradually 
passes into the position characteristic of the adult, but 
not infrequently it retains the simian position and the 
child is said to be club-footed, or, properly speaking, it 
has talipes equino-varus. Messrs. Parker and Shattock 
have clearly shown that the articular surfaces of the 
astragalus in cases of congenital talipes equino-varus 
retain the ape-like disposition, and it occurred to me 
that if this is constant, the fibular malleolus in children 
