DISSBOTION OF THE ANTEEIOR LIMB. 27 



and the origin of the extensor metacarpi magnus outwardly. It here 

 gives off branches to the extensor metacarpi magnus, extensor pedis, 

 extensor suffraginis, and flexor metacarpi externus ; and, much reduced 

 in size, it descends between the shaft of the radius and the extensor 

 pedis, and terminates in the extensor metacarpi obliquus. The nerve 

 to the flexor metacarpi externus is furnished after the branches to the 

 extensor pedis, and, passing outwards between the latter muscle and the 

 bone, it penetrates its muscle at the radio-ulnar arch. 



Directions. — In this stage of the dissection the student will be better 

 able to trace the musculo-cutaneous branch of the median nerve, and the 

 insertions of the biceps and brachialis anticus muscles (see pages 16 and 

 19). When these have been examined he may, as the next step, either 

 dissect the articulations of the shoulder and elbow (pages 43 and 45), or 

 he may saturate the parts already dissected with some preservative 

 solution, and postpone the examination of these joints till after the 

 dissection of the metacarpus and digit. 



THE METACABPUS AND DIGIT. 



The distal portion of the horse's fore limb, beyond the lower extremity 

 of the radius, is technically termed the manus, as it corresponds to the 

 hand of man. The carpus, or, as it is commonly but erroneously termed, 

 the knee, of the horse corresponds to the wrist of the human subject. 

 The portion of the limb between the carpus and the fetlock, representing 

 the palmar portion of man's hand, is called the metacarpus ; while the 

 rest of the limb, beyond the fetlock, is the digit, and is the homologue 

 of man's middle-finger. 



Surface-marJcing. — By flexing the carpal and fetlock joints, the splint 

 bones may be felt at the back of the metacarpus. Behind the bones in 

 the same region lie the flexor tendons, the subcarpal ligament, and the 

 suspensory ligament. These, whose edges may be more or less distinctly 

 seen in a well-bred animal, have the relation to each other shown in 

 Plate 7. Behind the fetlock-joint is a tuft of hair in which will be 

 found a horny spur or ergot, which is largest in coarse-bred animals. 

 By manipulation, the flexible lateral cartilages may be felt above the 

 hoof, in the region of the heels. 



Directions. — The entire remaining portion of skin should now be care- 

 fully removed from the limb. Should it be intended to study from the 

 same preparation the parts contained within the hoof, this must, before 

 the removal of the skin, be detached by force in the manner described 

 on page 35. The various structures are now to be defined by dissection 

 in the order of the following description ; and, while the vessels and 

 nerves are being cleaned, care must be taken of the small lumhricales 

 muscles, which lie on the tendon of the deep flexor above the fetlock. 



