DISSECTION OF THE DOG 135 



projecting extremity of the pisiform bone it forms a transverse band associated 

 with the tendon of the ulnar extensor. Between the fascia and the bone there 

 is a synovial membrane, already mentioned. 



The fascia of the palmar aspect of the manus is connected intimately with 

 the various callosities and with the annular bands of the flexor tendons. 



Superficial veins of the palm. — The proper digital veins unite with a 

 venous arch at the distal part of the metacarpus. From the radial end of the 

 arch there arises a large vessel which forms the root of the ulnar vein and one of 

 the roots of the radial vein. At the ulnar extremity of the arch the superficial 

 veins communicate with the deep vessels. 



As in front, so at the back of the forearm the muscles are arranged in two 

 layers. The superficial layer contains four muscles which, enumerated from the 

 medial towards the lateral side, are as follows : Mm. pronator teres, flexor 

 carpi radialis, flexor digitorum sublimis, and flexor carpi ulnaris. Strictly 

 speaking, however, the ulnar flexor has only one of its heads, and that the 

 smaller, in the superficial layer. The humeral head of the muscle really forms 

 an intermediate layer, and is to be sought for underneath the superficial flexor 

 of the digits. 



M. pronator teres. — The round pronator is placed on the medial side of 

 the elbow-joint, and, with the supinator muscle, circumscribes a triangular 

 space the base of which is proximal. In the triangle are found the insertions 

 of the brachial and biceps muscles, the median and deep radial nerves, and the 

 brachial vessels. 



The pronator teres muscle has origin from the medial epicondyle of the 

 humerus, and is inserted about the middle of the medial border of the radius 

 superficial to the attachment of the supinator. 



M. flexor carpi radialis. — The radial flexor of the carpus is a relatively 

 small muscle arising from the medial epicondyle of the humerus between the 

 pronator teres and the flexor digitorum profundus. About the middle of the 

 forearm the muscle is succeeded by a thin rounded tendon which, after crossing 

 the flexor aspect of the carpus, divides into two parts to be inserted into the 

 bases of the second and third metacarpal bones. A reinforcing band leaves 

 the middle of the medial border of the radius and joins the tendon of this 

 muscle. 



M. flexor digitorum sublimis. — The superficial flexor of the digits is a 

 large flattened muscle separated from the foregoing by a narrow strip of the 

 deep flexor. Its origin is from the medial humeral epicondyle. In the distal 

 part of the forearm a strong tendon passes over the flexor aspect of the carpus 

 just medial to the pisiform bone. Arriving in the palmar region this divides 

 into four parts, each of which, after splitting for the passage of the deep 

 flexor tendon, finds insertion into the second phalanx of a digit. 



k4 



