J. Playfair McMurrich 183 
It passes obliquely inwards between the flexor carpi radialis and the 
radius and soon divides into a superficial and a deep branch. The 
ramus profundus (Fig. 1, rp) passes behind the pronator quadratus, 
which it supplies, and descends the arm in that position to the lower 
edge of the muscle, where it comes to lie immediately below, 7. ¢. dorsal 
to the palmaris profundus I to which it sends fibres. 
The superficial branch passes toward the median line of the arm 
ventral to the pronator quadratus, and divides into two branches after 
giving a twig to the flexor carpi ulnaris and to the epitrochleo-anconeus. 
The two branches may be termed the ramus ulnaris (rsw) and the 
r. medialis (rsm). The former gives off a second branch to the 
flexor carpi ulnaris and passes obliquely across the ventral surface of 
the ulno-carpalis, which it supples, and then descends the arm upon 
the ulnar side of that muscle. In Amblystoma it hes in the lower 
part of the forearm between the ulno-carpalis and the palmaris profun- 
dus III, and, as it nears the carpus, it bends ulnarwards between the 
latter muscle and the ulna and comes to lie superficially upon the ulnar 
side of the arm. In Plethodon, however, in which the origin of the 
palmaris profundus III does not extend so high upon the arm, the 
nerve begins to bend ulnarward before it reaches the origin of the 
muscle and consequently possesses somewhat different relations to it 
than it does in Amblystoma. 
The medial ramus breaks up into a number of branches which 
ramify in the substance of the palmaris superficialis, one, however, 
descending a short distance to give off a branch to the palmaris profun- 
dus II and also to the palmaris profundus III. 
The supply of the various amphibian muscles may be tabulated, then, 
as follows: | 
Epitrochleo-anconeus 1 
Flexor carpi ulnaris R. superficialis ulnaris. 
Ulno-carpalis \ 
Palmaris superficialis q 
Palmaris profundus II 
R. superficialis medialis. 
Palmaris profundus III \ 
Palmaris profuydus I 
Pronator quadratus R. profundus. 
Flexor carpi radialis 
In the reptilia the main nerve stem for the flexor muscies of the 
forearm enters from above upon the radial side and, as in the amphibia, 
may be termed the N. brachialis longus inferior. It early divides into 
two stems, a ramus profundus and a R. superficialis, whose generai 
relations are practically identical with those found in the amphibia. 
