J. Playfair McMurrich 179 
the mouse and man, employing for my serial sections advanced embryos 
of these forms instead of adult individuals, simply as a matter of con- 
venience in preparation. I made use of von Ebner’s decalcifyitg solu- 
tion, embedded in paraffin, cut to a thickness of 20 4% and stained on the 
slide either with picrolithium carmine or with Delafield’s hematoxylin 
followed by van Gieson’s picrofuchsin, this latter method giving excel- 
lent differentiation of the various tissues. 
I. Tue Forearm FLEXors OF THE URODELOUS AMPHIBIA AND - 
LACERTILIA. 
It is well known that the flexor muscles of the forearm of the urodele 
amphibia may be regarded as consisting of three layers. The most 
superficial layer consists of muscles arising from the internal condyle 
of the humerus and extending longitudinally to be inserted either into 
the carpus or into a strong palmar aponeurosis; the middle layer is 
made up for the most part of oblique muscles arising from the ulna 
and passing distally and radially to be inserted into the palmar apo- 
neurosis, one muscle only, the ulno-carpalis, having an almost longitu- 
dinal direction and being inserted into the carpus; while the third 
layer consists of a sheet extending obliquely across between the ulna 
and radius. 
The superficial layer is divided into three or four muscles; (1) the 
palmaris superficialis (Fig. 1, PS), which occupies the median portion 
of the layer and inserts into the palmar aponeurosis, (2) the flexor 
carpi ulnaris (F. C. U.), (3) the flexor antibrachti ulnaris (epitrochleo- 
anconeus), Eisler, which inserts into the ulna and is more or less per- 
fectly differentiated in different forms, and (4) the flexor carpi radialis 
GEC: he). 
The oblique muscles of the middle layer are divided by the ulno- 
carpalis into an ulnar and a radial portion, the latter being again more 
or less distinctly divided into two portions, so that altogether the layer 
is composed of four muscles. The most ulnar of these and therefore 
the most superficial may be termed the palmaris profundus III (Hisler) 
(P. P. II) ; it arises from the ventral surface of the lower part of the 
ulna and is inserted into the under (dorsal) surface of the palmar 
aponeurosis. To the radial side of it and separating it at its origin 
from the palmaris profundus II is the wlno-carpalis (U.C.), which, 
arising from the ulna, descends almost longitudinally to be inserted 
into the distal row of carpal bones. More radially lies the palmaris 
profundus II (P.P.1L) which resembles closely the palmaris profun- 
