J. Playfair McMurrich 205 
On the other hand a very strong aponeurosis (vc), frequently partly 
transformed into cartilage, is present beneath the flexor superficialis, 
giving origin to this muscle from its palmar surface and receiving the 
insertion of the forearm muscles as described on a preceding page. 
We may for convenience confine our attention mainly to the muscles 
associated with the three middle digits, for the same reason that led us 
to disregard the lateral digits in the amphibia. 
Traced distally the central portion of the superficialis sheet divides into 
three portions (Fig. 11, F. B.8.), which pass to the three digits we are 
considering, and underneath each 
portion there is a strong tendou 
which is a distal continuation of 
the volar cartilage. Shortly before 
reachingthe metacarpo-phalangeal 
joint each portion of the super- 
ficialis splits into two slips, which 
separate so as to le one on each 
side of the strong tendon just 
mentioned and gradually fade out 
into the fascia covering that ten- 
don. 
The muscles which correspond 
to the amphibian flexores breves 
medii reach a much greater devel- 
opment than in the lower group 
and are arranged in two distinct 
layers, the superficial one (Fig. 
11, /) lying immediately beneath 
the volar cartilage, from which it palm of Ltoleplama Intenniane Fe epee 
ines omgins while: the deeper= 02 ¢° supeskolals ie or ths eee 
ene (ue) ig im velation with’ the Grtnoderoriaevs ceding ne aie ee 
underlying metacarpal bones. 
This latter layer does not concern us at present and will be left for con- 
sideration on another occasion. The superficial layer when traced distally 
divides into four portions which pass to the II-V digits, there being no 
portion for the pollex. Each portion lies beneath the corresponding 
portion of the flexor superficialis, being separated from it by the strong 
tendon derived from the volar cartilage. More distally each of the por- 
tions corresponding to digits II-IV divides into two slips which come to 
lie on either side of the corresponding strong tendon and are finally in- 
serted into opposite sides of the base of the metacarpo-phalangeal fibro- 
cartilage of the digit to which they belong: 
14 
