142 DISSECTION OF THE DOG 



bone and gives place to a thin tendon at the proximal part of the metacarpus. 

 The insertion of the abductor is into the lateral aspect of the base of the first 

 phalanx of the fifth digit, and into the lateral sesamoid bone. 



M. flexor digiii quinti brevis. — The short flexor lies medial to the abductor, 

 and has origin from the strong ligamentous band which joins the pisiform 

 bone to the third and fourth metacarpals. Its slender tendon joins that of 

 the abductor. 



Dissection. — The deep vessels and nerves of the palm must now be examined. 

 The continuation of the ulnar artery runs under the ligamentous band 

 which joins the pisiform to the third and fourth metacarpal bones, and 

 then under the short flexor of the fifth digit. To follow it, it is necessary 

 to reflect the adductors of the second and fifth digits as well as the 

 interosseous muscle of the second digit. This dissection will also expose 

 the continuation of the ulnar nerve. 



Arcus volaris profundus. — The deep volar arch is formed under the 

 short muscles of the digits in the proximal third of the metacarpus, by the 

 union of the continuation of the ulnar artery and the termination of the radial 

 artery. The radial artery gains the arch by passing under the short muscles of 

 the first digit. 



From the arch arise volar metacarpal arteries (aa. metacarpeae volares II, 

 III, et IV) which run distalwards between the second and third, third and 

 fourth, and fourth and fifth metacarpal bones. The third artery is the largest 

 and most superficial. 



At the distal end of the metacarpus the volar metacarpal arteries are 

 connected with the common dorsal digital arteries. 



Ramus profundus of the ulnar nerve. — The deep branch of the 

 ulnar nerve follows the ulnar artery into the palm and is there related to the 

 deep volar arch. Filaments are supplied to the deep muscles of the palm, and 

 three common volar digital nerves (for the second, third, and fourth digits) are 

 also furnished. The common volar nerves follow the arteries of the same 

 name, and, at the distal end of the metacarpus, divide into the proper digital 

 nerves (nn. digitales proprii) for the adjacent sides of neighbouring digits. 



Dissection. — It now only remains to examine the various joints of the limb. 

 Remove the muscles and remains of fascia, etc., and begin the dissection 

 of the articulations with the shoulder-joint. 



Articulatio humeri. — The necessity for many or powerful ligaments in 

 connection with the shoulder-joint is obviated by the numerous strong 

 muscles closely surrounding the articulation. Indeed there is only a joint- 

 capsule (capsula articularis) attached to the margin of the glenoid cavity of the 



