THE LIMBS OF THE HOUSE 55 



Roughly on a level with the middle of the first phalanx there is 

 a depression bounded by the bone and the flexor tendons. Lastly, the 

 region adjoining the hoof on each side of the digit should be manipulated 

 to detect the presence of normally resilient cartilaginous extensions of 

 the third phalanx. 



Dissection. — Having made a careful examination of the surface, now 

 remove the skin, and in doing so exercise caution lest the vessels and 

 nerves of the region should be injured. Pay particular attention to the 

 disposition of the deep fascia. 



In cleaning the surface of the flexor tendons do not remove the 

 lumbrical muscles that lie along the side of the tendons in the distal 

 part of the metacarpus. 



Fascia of the metacarpus and digit. — The deep fascia of the 

 metacarpus and digit (fascia metacarpea et digitalis) demands special 

 attention because of its notable strength and characteristic disposition 

 on the volar aspect of the limb. 



In the proximal part of the metacarpus a strong sheet, continuous 

 with the transverse carpal ligament, crosses from the second to the 

 fourth metacarpal bone and closely invests the flexor tendons. On the 

 volar aspect of the digit are well-marked transverse bands that form 

 sheaths for the flexor tendons and retain them in position. Opposite 

 the metacarpo-phalangeal joint a volar annular ligament assists the 

 sesamoid bones, to which it is attached, in the formation of a fibro- 

 osseous canal through which the flexor tendons play. Immediately 

 distal to this is a four-sided sheet of fascia, adherent to the surface 

 of the superficial flexor tendon and fixed by bands to the ends of the 

 medial and lateral borders of the first phalanx. This is the vaginal 

 ligament of the flexor tendons. 



A third annular band, only partially visible at the present stage of 

 the dissection, is associated with the terminal part of the deep flexor 

 tendon, between which and the digital torus the greater part of it is 

 interposed. In general outline the band is crescentic, the horns of the 

 crescent being represented by strong fascial strands attached about the 

 middle of the borders of the first phalanx. Connected with each side 

 of this part of the tendon sheath is the so-called ligament of the ergot, 

 which, beginning as a comparatively narrow band in the fibrous basis of 

 the " ergot," crosses the digital artery and nerve obliquely, widens at the 

 side of the joint between the first and second phalanges, and merges 

 into the third annular band of fascia. 



M. extensor digitorum communis. — The tendon of the common 

 extensor has been followed over the distal end of the radius and the 

 dorsal face of the carpus. It continues along the front or dorsal surface 

 of the metacarpus and digit and ends at the extensor process of the 



