82 TOPOGRAPHIC AND APPLIED ANATOMY. 



FIG. 34. A longitudinal section through the region of the elbow and the humero-ulnar articulation (frozen section). 



flexor carpi radialis is visible. The "pulse" of the radial artery may usually be felt just to the 

 outer side of this tendon. The pulsation of the ulnar artery is scarcely, if at all, perceptible, since 

 this vessel is covered by the border of the flexor carpi ulnaris muscle (see Fig. 35). The tendon 

 of this muscle may be palpated and the incision for exposing the artery may consequently be 

 easily located. 



Muscles. The muscles of the forearm should be reviewed in detail from a systematic 

 anatomy. The flexor group may be subdivided into a superficial and a deep layer, each consist- 

 ing of four muscles. All of the superficial flexors originate from the internal condyle. The 

 pronator radii teres is inserted into the outer surface of the middle of the radius. The flexor 

 carpi radialis is attached to the base of the second metacarpal bone. The palmaris longus 

 radiates into the palmar fascia. The flexor carpi ulnaris, the ulnar origin of which extends 

 downward to the lower third of the bone, is inserted into the pisiform bone, the unciform process 

 of the unciform bone, and the base of the fifth metacarpal bone. 



There are four deep muscles upon the flexor surface. The flexor sublimis digitorum arises 

 by two heads from the internal condyle of the humerus and from the anterior surface of the 

 radius and is inserted by means of four tendons into the second phalanges of the fingers. [This 

 muscle arises by three heads, one from the inner condyle of the humerus, one from the inner 

 margin of the coronoid process of the ulna, and one from the radius. ED.] The flexor 

 profundus digitorum arises from the upper two-thirds of the anterior surface of the ulna [also 

 from inner surface. ED.] and from the interosseous membrane and is inserted by means of four 

 tendons into the terminal phalanges of the fingers. The flexor longus pollicis arises from the 

 anterior surface of the radius, from the interosseous membrane, and by a small muscular slip 

 from the internal condyle and is inserted into the terminal phalanx of the thumb. The pronator 

 quadratus, situated above the wrist, arises from the anterior surface of the ulna and is inserted 

 into the anterior and outer surface of the radius. 



The extensor muscles are subdivided into a radial group and a dorsal group. 



The radial group consists of four muscles, which arise from the external condyle and from the 

 humerus above this point. The supinator longus is inserted into the styloid process of the radius. 

 The extensor carpi radialis longior runs to the dorsal surface of the base of the second meta- 

 carpal bone. The extensor carpi radialis brevior goes to the dorsal surface of the base of the third 

 metacarpal bone. The supinator brevis, originating also from a ridge upon the ulna, passes over 

 the radius and is inserted above and below the tuberosity upon its anterior surface. 



The dorsal group of extensor muscles, like the flexor group, may be divided into a super- 

 ficial and a deep layer. The superficial layer consists of three muscles. The extensor carpi 

 ulnaris arises from the external condyle, from the deep fascia of the forearm, and from the posterior 

 border of the ulna, and is inserted into the base of the fifth metacarpal bone. The extensor com- 

 munis digitorum arises from the external condyle and from the deep fascia of the forearm and is 

 inserted by means of four tendons into the dorsal aponeuroses of the fingers. The extensor 

 minimi digiti arises from the external condyle and furnishes a second tendon to the little finger. 



The deep layer of the extensor muscles arises from the dorsal surfaces of the ulna, radius, and 



