J. Playfair McMurrich 203 
In Amblystoma, for example, as a series of sections is traced distally, 
one finds some distance above the wrist a layer of fascia making its 
appearance upon the palmar surface of the palmaris superficialis. This 
is the palmar aponeurosis, and it is into the deep (i.e. the dorsal) surface 
of this that the superficialis inserts. More distally the aponeurosis 
receives the insertion of the palmares profundi, also upon its deep 
surface, and immediately distal to this insertion one finds some muscle 
bundles making their appearance in the substance, as it were, of the 
aponeurosis. These bundles represent the proximal portion of the origin 
of the flerores digitorum breves superficiales (Hisler), and in more distal 
section they increase in number and form a continuous sheet (Fig. 9, 
F. B. S.), which divides the palmar aponeurosis into two layers, a 
more superficial one (p. a. s.) lying ventral to the flexores and a deeper 
one (p. a. d.) dorsal to them. The muscle sheet soon divides longi- 
tudinally into three portions, the more lateral parts, destined for the 
second and fifth digits, separating for a median part destined for the 
third and fourth fingers. On account of the divergence of the second 
and fifth digits from the median line a series of sections transverse to 
the axis of the forearm will, when continued into the hand. cut these 
digits obliquely, so that the relations of their muscles cannot be as 
readily perceived as those of the third and fourth digits; for the present, 
therefore, attention will be directed solely to the arrangement of the 
muscles and apeneuroses belonging to these latter digits. 
Immediately beneath the deep layer of the palmar aponeurosis and 
arising from its deep surface are the flevores digitorum breves medir 
(Kisler) (F. B. M.), while below these again and resting directly upon the 
palmar surfaces of the metacarpal bones from which they arise are the 
flexores digitorum breyes profundi (F. B. P.). Finally, stretching across 
between the metacarpals are the intermetacarpales (1. M.). The flexores 
superficiales and medii are the muscles which especially interest us just 
now and they may be briefly described as follows, so far as the portions 
which pass to the third and fourth digits are concerned. At the junc- 
tion of the proximal and distal halves of the metacarpals the superficialis 
sheet divides into two portions corresponding to the two digits, and at 
about the same time a longitudinal division of the superficial layer of 
the palmar aponeurosis occurs, a strong slip of it being contained distally 
upon the palmar surface of each superficialis slip (Fig. 10), while 
beneath each superficialis slip a thickening appears in the deep layer of 
the aponeurosis. More distally the lateral portions of each superficialis 
slip separate (Fig. 10, F. 8.’) and pass dorsally to fuse with the corre- 
sponding flexor brevis profundus (F.P.}, while the remaining median 
