PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
19 
point. It frequently joins the curve described at the base of the great 
toe. The great obliquity of this groove in the human foot is due not 
to the fact that the toes flex towards the great toe (compare the de- 
scription of the hand) but to the fact that the metatarsal bones of the 
toes become progressively shorter as we proceed to the fifth digit, the 
groove in question lying over the heads of the metatarsal bones. 
Let us now compare the foot of the Orang with that of man. The 
markings in the sole of the foot in the Orang are more distinct than in 
man because the animal does not obliterate them in walking, during 
which the outer margin of the foot alone comes to the ground; the outer 
margin is in consequence smoother than the remaining portion of the sole. 
We are at once struck by the great length of the four outer toes, they 
are long, and are separated from one another so as to resemble fingers 
rather than toes. The great toe in the Orang’s foot, however, presents 
a remarkable difference from the hallux in man. Thus in the Orang 
it is very much shorter than the other toes, and its long axis forms 
a marked angle with the long axis of the remaining part of the foot. 
It is capable in fact of being placed at right angles to the long axis of 
the sole. The metatarsal bone of the great toe is not connected by a 
transverse metatarsal ligament to the second digit, and in this respect 
also differs from the human foot. The ball of the great toe in the Orang 
(as observed in the photograph) is marked off by a well marked groove^ 
but this groove is not opposite the metatarso-phalangeal joint but opposite 
the tarso-metatarsal joint and marks off the mass of muscular tissue which 
lies in relation to the plantar aspect of the metatarsal bone. In other 
words the line is associated with adduction and opposition, and in this 
respect entirely corresponds to the line described in connection with 
that movement in the human hand or in the hand of the Orang itself 
The lines running across the sole at the bases of the other digits are 
oblique and very similar in their position and characteristics to those 
observed in the palm of the hand. The obliquity here may partly be 
accounted for by the gradual diminution in length of the digits as we 
proceed from the second to the fifth digits, but is also accounted for 
by the fact that the Orang flexes its toes not directly into the sole, but 
somewhat towards the hallux, the mark being at right angles to the 
line of movement in flexion. The lines corresponding to the flexion of 
the digits themselves are well marked opposite the metatarso-phalangeal 
and the interphalangeal joints. Note that in the Orang the line 
indicating flexion of the hallux at the metatarso-phalangeal joint is 
well marked, but is separated from the sole proper and lies upon the 
plantar aspect of the hallux itself, differing thus in its position and 
