LO THE STRUCTURE OF MAN 
begun to degenerate from the time that the plantar fascia became 
secondarily attached to the caleaneum, and helped in the forma- 
tion of the arch.of the foot, as the latter became transformed 
into a supporting organ. | : 
But why are the palmaris and plantaris of Anthropoids, 
in which such transformations do not take place, also in a 
degenerate condition? It does not appear difficult to answer 
this question if we consider that these muscles originally 
extended, as do their homologues in the lower Mammals, — 
through the mediation of the palmar or plantar fascia to the 
phalanges, and acted as common flexors of the fingers and toes. 
If so, in the course of time—to confine our attention to the 
hand—as the flexores digitorum communis superficialis and pro- 
fundus became more extensively and more subtly differentiated 
from the primitive “ pronato-flexor mass ” (Humphry), the fibrous 
terminal expansions of the palmaris withdrew more and more 
from the fingers, and found points of attachment in the palm of 
the hand and in the lhgamentum carpi transversum. Thus 
would the finger flexor appear to have become a hand flexor. 
As such, however, it could not, on account of its attachments, 
develop the same strength as the proper hand flexors,? which are 
directly attached to the skeleton, and which, as we see where 
the palmaris is wanting, are competent alone to bend the hand. 
The palmaris becoming thus superfluous, is variable and occasion- 
ally absent. 
A further consequence of the transformation of the hind-limb 
into a supporting and ambulatory organ, is that some of the 
flexor muscles which originally ran down without interruption to 
the sole of the foot. have become interrupted at the protuberantia 
calcanei by the dorsal flexion entailed. Another muscle of this 
flexor series, ¢.g. the short flexor, which corresponds with the 
flexor digitorum communis superficialis of the hand, has shifted 
its point of origin farther and farther down, till at last, on the 
acquisition of the upright gait, it has reached the calcaneal 
tuberosity. In doing so this muscle has become more and more 
closely connected with the plantar fascia; and at present it 
shows in many ways, e.g. in the variation of its terminal tendons 
' It is said that in Negroes the palmaris is still not infrequently inserted into 
the metacarpals. 
* That it is still functional in the hand is shown by its occurrence, which must 
still be considered normal. It is absent on one or both sides in about one in every 
ten bodies. 
