PRIMROSE : THE ANATOMY OF THE ORANG OUTANG. 
85 
established between the ape and man is one to which we have already 
called attention, namely, that in the human foetus we find correspond- 
ences more marked than they are when the adult man is compared with 
the ape. Cunningham mentions Ruge’s work in the following re- 
ference.^ “Ruge in his memoir upon the development of the muscles of 
the human foot shows that the interossei muscles in the foot of the early 
embryo are plantar in position, and that the upward growth of the 
dorsal interossei and the formation of the interosseous spaces takes place 
as a subsequent and gradual step. In three of the diagrams which illus- 
trate the text he gives representations by sections through the metatarsus 
at three different periods of development. In the first the metatarsal 
bones, with the exception of the first two, are in close apposition, and in 
consequence, all the interosseous muscles, excepting the first dorsal, are 
plantar in position. The second diagram is from a foot somewhat more 
advanced. It shows that as development progresses the metatarsal 
bones separate from each other, and that simultaneously with this the 
dorsal interossei begin to shoot up between them like wedges. The 
third illustration gives a view of the relative position of the muscles and 
metatarsal bones, as they are to be seen in the adult. The bones are 
widely apart from each other, and the muscles have reached the dorsum 
of the foot.” 
The transverse section (Plate IV, fig. 4), illustrates the fact that the 
interossei muscles are more plantar (palmar) than dorsal in my Orang ; 
this condition is exaggerated in the lower apes where, as I have already 
stated, Huxley found among the Platyrrhini the interossei of the foot 
were no longer visible from the dorsum but existed as flexores breves 
towards the plantar surface. In the dog the metatarsals are closely 
compressed, and the interossei wholly plantar. 
In the human foetus the great toe is separated from the other toes 
and the position of the foot is that of “varus,” resembling somewhat that 
found persistent in the ape. We find that this fact is alluded to by 
Flower,^ who, in referring to the principal difference between the foot of the 
ape and the foot of man, emphasizes the fact that in the ape the foot is 
converted into a more or less modified grasping organ. He directs 
attention to the effect produced upon the ape’s foot in consequence of 
the fact that the articular surface of the internal cuneiform for the hallux 
is saddle-shaped, and is directed obliquely towards the inner or tibial side 
1 Quotation rom Cunningham’s Challenger Report, p. 138-9. 
2 Loc. cit., p. 341. 
