182 The Phylogeny of the Forearm Flexors 
occupying the interval between the more median head of the flexor carpi 
ulnaris and the flexor carpi radialis (F.C.R.), and the other two 
(P. P. If and IIT) are deeper, one resting immediately upon the ventral 
surface of the ulna, while the other lies ventral to the pronator qua- 
dratus (P.Q.) and the radius. The fifth portion (Fig. 3, P. P.I) is 
short and is an oblique muscle arising from the ventral surface of the 
ulnar side of the carpus. All five portions insert distally into the 
palmar aponeurosis, which, in the 
majority of the forms studied, con- 
tains a strong volar cartilage. Prox- 
imally the superficial portions take 
origin from the internal condyle, 
while the deeper portions arise from 
the ulna or, in the case of the fifth 
portion, from the ulnar side of the 
carpus. 
On the radial side of the arm 
are two muscles, a more superficial 
flexor carpi radialis (F. C. R.) and 
a deeper pronator radu teres (P.'T.) 
both of which arise from the inter- 
nal condyle of the humerus, the 
former having its insertion into the 
radial side of the carpus and into the 
base of metacarpale I, while the lat- 
ter inserts into the lower part of the 
Fig. 3. Transverse section through the radial side of the radius. 
wrist of Liolepismalaterale. F.C. R., flexor : A é 
real ee Gee we Finally, constituting the deepest 
posse pe the Wie eran as Ka, layer, there is a pronator quadratus 
supose ulnaris; UL, ulnar; ve, volar (ie Q.) t extending between the 
radius and ulna, and in the proximal 
part of the arm a pronator accessorius (Mivart), which arises from the 
internal condyle and is inserted into the radius. 
Before proceeding to a comparison of the individual muscles of the 
amphibia and reptilia a description of the nerves of the forearm in the 
two groups will be necessary. For they present a remarkable similarity 
in their arrangement and will serve as guides in the determination of 
some of the more obscure homologies. 
In the amphibia the flexor muscles of the forearm are supplied by a 
large trunk which enters from the brachium towards the radial side and 
constitutes what has been termed the N. brachialis longus inferior. 
