120 THE OSTEOLOGY AND MYOLOGY 



slender and delicate, like silken threads, somewhat liable to be overlooked or destroyed, 

 unless carefully sought for. In passing the wrist they are confined by the annular liga- 

 ment, but are not included in the single large tendinous bundle just described. Contrary 

 to what is the case with the deep flexor tendons, these superficial ones may be easily sep- 

 arated from each other as high up as the muscular part, or even further. After reaching 

 the fingers each one splits, as in man, to embrace a deep flexor tendon ; the forked extrem- 

 ity is inserted into either side of the base of the second digital phalanx. The tendons are 

 also slightly bound down where they pass the bases of the fingers. 



Extensor digitorum communis. — (Fig. 30, d.) Proceeding down the external condyle, 

 we find the origins of three muscles appertaining to the posterior brachial region, besides 

 the three of the radial region already described. They are superficial, and pass straight 

 down the forearm ; the other muscles upon the back of the forearm are deep seated and 

 oblique in direction. The common digital extensor is the first of tliis superficial set, arising 

 from the external condyle next below the extensor carpi radialis brevior, and lying be- 

 tween this muscle and the proper extensor of the little finger. It is incompletely divisible 

 into two parts ; one for the index and middle, the other for the ring and little fingers ; but 

 aU four tendons can be separated high up on the arm. The four separate from each other 

 upon the back of the wrist, and each one proceeds to be inserted into the back of the base 

 of the ungual phalanx of a finger. As they pass the bases of the fingers all are bound 

 down by, or rather spread on either side to help form, the fascia of the parts. 



Extensor minimi digiti. — (Fig. 30, e.) Perfectly distinct from the foregoing, with which 

 it agrees in shape, but is rather smaller. It arises next below on the external condyle, 

 from the extreme anterior point of the latter. Its extremely delicate tendon runs along- 

 side that of the preceding to the same insertion, and is sometimes virtually, if not actually, 

 blended with it. Before reaching the finger it frequently gives off a filamentous slip that 

 joins the extensor tendon of the annularis. 



Extensor carpi idnaris . — (Fig. 30, /.) Scarcely larger than either of the preceding; 

 lying superficial along the edge of the ulna, arising from the lowest point of the external 

 condyle and contiguous part of the joint, and for a short distance from the ulna itself, be- 

 coming tendinous midway, running along a slight groove in the head of the ulna to be in- 

 serted into the base of the fifth metacarpal. 



Extensor indicis [et pollicis). — (Fig. 30, g.) Proper extensors of the first and of the 

 second pollical internodes do not exist ; but the extensor of the fore finger has two per- 

 fectly distinct tendons, one of wdiich goes to the thumb and supplies the place of the 

 extensor secundi internodii pollicis. The muscle lies deep seated on the shaft of the ulna, 

 covered by the ulna carpal extensor, and is small and inconspicuous. It has no condylar 

 origin, arising from the upper half or third of the ulnar crest. Its two long, delicate ten- 

 dons gain the radial side by passing diagonally across the lower third of the forearm, un- 

 derneath the digital extensor tendons. One (ib. g") runs along the back of the forefinger 

 to the base of the ungual phalanx, side by side with the index tendon of the common 

 extensor, and virtually, if not actually, blended with the latter. The other (ib. g) passes 

 still more obliquely to gain the thumb along the back of which it runs, to be inserted into 

 the base of the distal phalanx. This thread-like tendon is the only extensor of the polhcal 

 internodes. 



Extensor ossis metacarjn pollicis. — (Fig. 30, h.) This muscle is of great size, as if to 



