212 



OSTEOLOGY. 



FLEXOR DIGITORUMSUBLIMIS 

 PKONATOR TERES 

 BRACHIALIS \ 



FLEXOR POLLICIS LONGUS "\ N 

 BICEPS 



subcutaneous throughout its whole length, and a volar margin (O.T. anterior 

 border). 



The crista interossea (interosseous crest) is crisp and sharp in the proximal 

 three-fourths of the body, but becomes faint and ill-defined in the distal 

 fourth. To this, with the exception -only of the part which forms the dorsal 

 boundary of the hollow in which the tuberosity of the radius is disposed when 

 the two bones are articulated, is attached the interosseous membrane which 

 connects the two bones of the forearm. The dorsal margin, of sinuous out- 

 line, curving laterally above, and slightly medially below, is continuous proxim- 



ally with the triangular subcutaneous area on 

 the back of the olecranon, being formed by the 

 confluence of the borders which bound that sur- 

 face ; well marked above, it becomes faint and more 

 rounded below, but may be traced distally to the 

 dorsal surface of the base of the styloid process. To 

 this border is attached an aponeurosis common to 

 the flexor carpi ulnaris, extensor carpi ulnaris, and 

 flexor digitorum profundus muscles. A noteworthy 

 feature in connexion with this part of the body is 

 the fact that it is subcutaneous, and can easily be 

 felt beneath the skin throughout its whole length. 

 The volar or anterior surface corresponds to 

 the front and medial side of the body. It ie 

 described as consisting of two surfaces, a volai 

 and a medial, which are separated by a rounded 

 volar margin, which extends from the tuber- 

 osity proximally towards the styloid process 

 distally. The prominence of this ridge varies 

 in different bones, being well marked in bones 

 of a pronounced type, but corresponding merely 

 to the rounding of the surfaces in poorly 

 developed specimens. The volar aspect of the 

 bone affords an extensive origin to the flexor 

 digitorum profundus muscle, which clothes its 

 volar and medial surfaces in its proximal three- 

 fourths, reaching as far back as the dorsal border, 

 and extending proximally as high as the medial 

 side of the olecranon process. Immediately distal to 

 the radial notch there is a hollow triangular area ; 

 limited dorsally by the proximal part of the inter- 

 osseous crest, and defined in front by an oblique 

 line which extends distally and backwards 

 from the lateral margin of the coronoid process. 

 In this hollow the tuberosity of the radius rests 

 when the forearm is in the prone position, and 

 to its floor are attached the fibres of origin of 

 the supinator muscle. The distal fourth of the 

 FIG. 204. VOLAR ASPECT OF BONES OF body is crossed by the fibres of the pronator quad- 

 THE EIGHT FOREARM WITH MUSCULAR rafcug musc l ej which derives its origin from a 

 ATTACHMENTS MAPPED OUT. ,, , n -, F. -, 



more or less well -denned crest, which winds 



spirally distally and backwards towards the volar surface of the root of the styloid 

 process, and is continuous proximally with the volar margin. 



The dorsal surface of the body lies between the dorsal margin and the in- 

 terosseous crest. At its proximal part it is placed behind the semilunar and 

 radial notches, extending on to the lateral side of the olecranon. Here an area 

 corresponding to the proximal third of the length of the bone is marked off dis- 

 tally by an oblique ridge which leaves the interosseous crest about an inch or 

 more distal to the dorsal edge of the radial notch. Into this somewhat 

 triangular surface the fibrp.a of the anconaeus are inserted. Distal to this the 



BRACHIO- 

 RADIALIS 



