1 8 PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
whilst in the adult they disappear. I have, however, photographed the sole 
of a child’s foot aged nine years (see reproduction of photograph), and find 
well marked all the lines described and figured by Robinson in the foot of 
the infant. I shall proceed to describe these lines and to enquire into 
their significance. In the child of nine years one is able to distinguish 
the lines which correspond to the oblique lines across the palm. In 
comparing the foot with the hand, however, one must bear in mind that 
the great toe (unlike the thumb) is parallel in position to the other 
digits, and that its metatarsal bone is closely united to the other digits 
by an extension of the transverse metatarsal ligament, whilst in the hand 
there is no such connection of the metacarpal bone of the thumb to the 
index finger. The hallux is therefore not free to move about in the 
manner characteristic of the thumb. Moreover the hallux cannot be 
opposed to the sole or to the other digits, and if we examine the muscula- 
ture in man we find there is no opponens hallucis. On examining the 
markings in the sole of the foot of the child (see photograph) we find a 
line strongly curved starting at the inner border of the foot at the base of 
the first digit, and passing outwards and forwards to terminate immedi- 
ately external to the cleft between the first and second digits, its point 
of termination separated 1.5 cm. from that cleft. This line marks off 
what is commonly called the ball of the great toe, but observe that the 
so-called ball of the great toe does not correspond with the ball of the 
thumb, in that the soft structures forming the ball of the great toe are 
related to the plantar aspect of the proximal phalanx of that digit ; 
whilst the ball of the thumb is formed by structures related to the 
palmar aspect of its metacarpal bone. This curved marking in the sole 
is therefore opposite the metatarso-phalangeal joint, and corresponds to 
the marking on the palmar aspect of the thumb opposite the metacarpo- 
phalangeal joint of that digit, and not to the curved marking at the 
base of the thenar eminence. This curved line in the sole therefore is 
produced by flexion of the hallux at the metatarso-phalangeal joint. 
If we look for any marking in the sole produced by opposition or 
adduction of the great toe in man we look in vain. There is no such 
marking, and therefore the characteristic mark found in the palm 
bounding the thenar eminence is wanting in the sole. We find, how- 
ever, a curved line across the sole beginning at the base of the second 
digit and running at first somewhat longitudinally for a short distance 
and then curving outwards to end at the outer border of the foot. This 
curved line is often interrupted in the sole, but can always be readily 
distinguished. It is frequently spoken of as limiting the ball of the 
little toe, but it too is opposite the metatarso-phalangeal joint and is 
therefore merely an indication of the flexion of the smaller toes at that 
