870 MR. ST. GEORGE MIVART ON THE [ Dec. 6, 
the pronator quadratus), and into the radial carpal ossicle, into which 
are especially inserted the fibres from the interosseous ligament. 
Pronator quadratus* (figs. 12 & 15, P. Q). This is small, and 
confined to the lower part of the forearm. It springs from the 
radial aspect of the ulna and from the lower part of its flexor surface, 
with the pronator accessorius superficial to it on the flexor aspect of 
the arm. It is inserted into the flexor aspect of the radius for about 
its distal fourth, but it does not go to the radial ossicle. It is alto- 
gether a transverse layer running directly from the ulna to the 
radius. 
Flexor carpi ulnaris (figs. 1, 8, 10, & 11, F.U). This muscle is 
much more distinct from the flexor carpi radialis than it is in the 
Iguana. It has a double origin—one from the internal condyle, the 
other (by a tendon common to it and the extensor carpi ulnaris) from 
the lower end of the back of the humerus. Passing downward, the 
two parts unite, but, before doing so, leave exposed one part of the 
flexor profundus digitorum, as another part of that muscle comes to the 
surface between the flexor ulnaris and flexor radialis. It is inserted 
into the palmar ossicle, and therefore superficially to the tendon of 
the extensor carpi ulnaris. 

Deeper flexor surface of right forearm. 
F. D. Flexor profundus digitorum. /. P. Flexor longus pollicis, FR. Flexor 
radialis. P.A. Pronator aecessorius. P. 7. Pronator quadratus. 
Flexor longus pollicis (figs. 8, 10, & 28, F. P). This large mus- 
cle has three distinet origins. The first is from the internal condyle, 
between the two tendons of origin of the flexor carpi radialis. ‘The 
second is from the internal condyle, below the first head of origin. 
These two parts soon unite to form one belly. The third head of 
origin springs from the olecranon and the radial aspect of the upper 
part of the ulna. It unites with the other belly about the middle of the 
forearm (where the ulnar nerve comes out over it), and passing distad 
ends in a strong tendon which divides into four, one division going to 
each of the three radial digits (pollex, index, and mid digit), and the 
fourth division uniting with that tendon of the flexor profundus 
digitorum which goes to the fourth digit. 
* Meckel, /.c. p. 369. 
