32 THE ANATOMY OF THE HORSE. 



liorse they arc of small but very vai-iable size. Frequently they contain 

 but little muscular tissue, but now and again a subject is met in which 

 they are very distinct. They are two in number, one being placed on 

 each side of the deep flexor tendon, above the fetlock. The fibres of 

 the small muscular belly (uise from the side of the deep flexoi-, and 

 terminate in a small tendon which is lost in the tissue beneatli the 

 horny spur of the fetlock. 



The IxTEROSSEi Muscles (Plate 9). These are the representatives 

 of the muscles which, in the human hand, fill up the interspaces of the 

 metacarpal bones, and give lateral movement to the fingers. In the 

 hoi'se they are two in number, and are extremely rudimentary'. Each 

 is to be sought to the inner side of the small metacarpal bone of its 

 own side, between that bone and the edge of the suspensory ligament. 

 Each has at its upper end a small muscular belly taking origin from 

 the neighbourhood of the head of the small metacarpal bone. It is 

 succeeded by a long, slender, nerve-like tendon, which at the fetlock 

 blends with the band sent from the suspensory ligament to the extensor 

 l>ediii tendon, or with the connective-tissue on the side of the joint, 



The interossei and lumbricales muscles are of great interest to the 

 comparative anatomist, but, from their small size, they can have no 

 appreciable effect on the movements of the digit. 



The Tendon of the Extensor Suffraginis (Plate 7) is to be followed 

 from the point below the carpus to which it has already been dissected. 



The flat tendon, after crossing the carpus, descends to the outer side 

 of the anterior surface of the large metacarpal bone. As it passes over 

 the fetlock-joint, it becomes somewhat broader, and its play over the 

 anterior ligament of the joint is facilitated by means of a small synovial 

 bursa. Immediately below the joint it is inserted into the fore part of 

 the upper end of the first phalanx. In the region of the metacarpus 

 the tendon receives on each side a reinforcing band. The outer band 

 comes from the external side of the carpus ; the inner is detached from 

 the extensor pedis tendon. 



Action. — The muscle is primarily an extensor of the digit on the meta- 

 carpus. When contraction is carried beyond this, it extends the meta- 

 carpus on the fore-arm. 



Tlie Tendon of the Extensor Pedis (Plate 7). This tendon, after 

 throwing off the slip to the extensor suffraginis, descends over the front 

 of the metacarpus and digit, and lies on the middle line. Its play over 

 the anterior ligament of the fetlock is fiicilitatcd by a small synovial 

 Ijursa ; while, over the front of the interphalangeal joints, the synovial 

 membrane is directly supported by the deep face of the tendon, there being 

 no anterior ligament for these joints. At the middle of the first jjhalanx 

 the tendon is joined on each side by a strong band which descends 

 obliquely over tlie side of the fetlock from the suspensory ligament. 



