MTOLO&T OP OPISTHOCOMUS CEISTATUS. 359 



Flexor carpi ulnaris is well developed. Origin similar to preceding muscles. 

 Insertion into the ulnar carpal bone. Arising in conjunction with the latter, also from 

 the olecranon of the ulna, is a moderately developed muscle, which is applied closely 

 against the bases of the five or six posterior ulnar wing-feathers. This terminates in a 

 long fibro-elastic tendon, and is connected to the bases of the remainder wing-feathers as 

 far as the carpus; this is the extensor carpi ulnaris. Immediately inferior to the latter 

 is another elastic tendon, which connects the bases of all the wing-feathers together, its 

 line of attachment corresponding to that of the integuments. It is strong, powerful, 

 and as elastic as a piece of india-rubber. Its action is to approximate all the wing- 

 feathers, and to maintain the carpus flexed on to the metacarpus. 



Flexor profundus digitorum. — Consists of two portions. The first arises from the 

 proximal two-thirds of the inner or flexorial aspect of the ulna, and terminates in a 

 common tendon, which grooves the carpus, and there divides into two tendons, — a short 

 and a radial one, which is inserted into the base of the distal phalanx of the 1st or rudi- 

 mentary digit ; the second or long one (internal to the preceding) goes to the distal 

 extremity of the second or long digit. The second portion is the flexor metacarpi 

 pollicis. 



It arises b)' fleshy fibres from the lower third of the ulna. It crosses obliquely over 

 the lower end of that bone, terminating in a short tendon which grooves the outer portion 

 of the carpus (the radial carpal). It is inserted into the superior and dorsal aspect of 

 the carpus adjoining the rudimentary 1st digit. It is a powerful flexor of the carpus. 



Muscles on the superior border of the Radius. 



The extensores carpi radialis longior et brevior are both closely associated at their 

 origin, and receive, respectively, a tendinous slip from the extensor plicae alaris. The 

 distal tendons of these two muscles unite opposite the lower end of the radius, to be 

 inserted into the base of the first metacarpal. The latter arrangement is common in 

 many mammals, and is occasionally found in Man. 



The extensor ossis metacarpi pollicis arises from the posterior surface of the upper 

 half of the shaft of the radius, and by a few fibres from the ulna. It is inserted by a 

 slender tendon into the base of the 2nd metacarpal immediately posterior to the con- 

 joined tendons of the extensors carpi radialis longior et brevior. A small rudimentary 

 interosseous membrane intervenes between the extensor and flexor muscles. 



The extensor indicis arises from the lower half of the shaft of the radius (from the 

 interosseous membrane) and from the adjoining portion of the ulna. It terminates in 

 a strong tendon, which grooves the lower end of the ulna, crosses beneath the innermost 

 tendon of the extensor communis digitorum to its ulnar side, and is finally inserted into 

 the base of the 2nd phalanx of the 2nd digit. 



The extensor longus digitorum consists of two muscles, both of which arise from the 

 external condyle. The radial one terminates in a slender tendon, which is inserted into 



