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The Phylogeny of the Forearm Flexors 
In the cat the condylo-ulnaris is not distinctly separated from the 
ulnaris in the upper part of the arm and it contains a tendon imbedde¢ 
in its substance which is continuous with a tendon on the ventral surface 
of the ulnaris. Apparently a portion of the condylo-ulnaris inserts 
into the ulnaris tendon and this unites with the other four portions. to 
form the profundus tendons as in the opossum, but the rest of the 
muscle, the shaded portion in Fig. 6, can be clearly seen to divide near 
the wrist into a smaller radial and a larger ulnar portion which remain 
distinct from the wlnaris and in each of which a tendon develops. The 
eo tendon belonging to the larger portion 
eventually divides into two slips which 
form the sublimis tendons for the 
third and fourth digits, the tendon for 
the smaller portion of the muscle pass- 
ing to the second digit. The fourth 
tendon, that for the fifth digit, is 
formed by a slp from the palmaris 
longus, the relations of the 
sublimis being very similar 
to what obtained in the 
contributed to it by the 
condylo-ulnaris is somewhat 
greater in the cat. 
In the mouse the condi- 
tions are somewhat differ- 
ent, however. As usual the 
five portions of the flexor 
mass and the  palmaris 
longus can be recognized 
Fic. 7. Transverse section through the forearm of a (Fig. ‘) and tracing them 
new-born mouse. Lettering as in Fig. 5. downward it ean be seen that 
the ulnaris, radialis, centralis and condylo-radialis all unite together to 
form a profundus tendon. But the condylo-ulnaris remains quite separate 
from the rest and at the wrist divides into three portions which, becom- 
ing tendons, pass as the perforated tendons to the second, third and fourth 
digits, there being in this form, or at all events in the single individual 
I studied, no sublimis tendon to the fifth digit and hence no contribu- 
tion to the sublimis from the palmaris longus. 
These three forms afford a very definite clue to the relations of the 
sublimis to the flexor communis. It is principally associated with the 
opossum, though the amount 
