DISSECTION OF THE DOG 141 



branches for the adjacent borders of neighbouring digits (aa. digitales volares 

 proprise). 



Mm. lumbricales. — Three slender lumbrical muscles arise from the palmar 

 aspect of the deep flexor tendon and He between the tendinous slips belonging 

 to second, third, fourth, and fifth digits. The middle muscle of the three is 

 the best developed. Their fine tendons are inserted into the radial side of the 

 proximal end of the first phalanx of the third, fourth, and fifth digits. 



Dissection. — Cut across the deep flexor tendon on a level with the carpus. 

 This will allow of the dissection of the deep muscles, etc., of the palm. 



Mm. interossei. — There are four fleshy and moderately large interosseous 

 muscles lying over the second, third, fourth, and fifth metacarpal bones and 

 in the grooves between them. They arise from the volar aspect of the distal 

 row of the carpus and from the proximal end of the metacarpal bones. Each 

 muscle divides into medial and lateral parts and is inserted to a pair of meta- 

 carpal sesamoid bones. In addition tendinous cords are continued to the 

 common extensor tendon. 



Short muscles op the first digit. — Three small, short muscles are 

 connected with the first digit. The most medial, m. abductor pollicis brevis et 

 opponens pollicis, is rudimentary and arises from the band which leaves the 

 sesamoid bone at the medial side of the carpus to join the tendon of the super- 

 ficial flexor. The abductor and opponens muscle is inserted into the distal 

 part of the first metacarpal bone and the proximal phalanx of the first digit. 

 M . flexor pollicis brevis is better developed than the foregoing, to the lateral side 

 of which it lies, and arises from the volar aspect of the carpus. The muscle 

 is inserted into the proximal phalanx of the first digit. The third short muscle 

 of the pollex, m. adductor pollicis, is the largest of the three. Its origin is from 

 the volar surface of the carpus between the foregoing and the interosseous 

 muscle of the second digit, and its insertion is into the lateral face of the 

 proximal phalanx of the first digit. 



M. adductor digiti secundi. — The adductor muscle of the second 

 digit is thin and narrow. Lying along the lateral border of the interosseous 

 muscle of the second digit, it has origin from the volar face of the carpus, and 

 is inserted into the first phalanx of the second digit. 



Short muscles of the fifth digit. — Four short muscles are connected 

 with the fifth digit. One of these, the interosseous, has already been described. 



M. adductor digiti quinti arises from the flexor aspect of the carpus close 

 to the origin of the adductor of the second digit. Crossing the interosseous 

 muscles of the third and fourth digits obliquely, it gains the first phalanx of 

 the fifth digit by sinking between the fourth and fifth interosseous muscles. 



M . abductor digiti quinti. — The abductor is the largest of the three muscles 

 now under consideration. It lies immediately under the skin on the lateral 

 border of the carpus. The relatively thick fleshy belly arises from the pisiform 



