352 DR. C. F. SONNTAG ON THE AiSTATOMY, 



The extensor indicis arises from the inner surface of the lower 

 fifth of the radius, and some fibres blend with the extensor longus 

 pollicis. Its long, and very slender tendon blends with the 

 dorsal expansion of the communis tendon to the index over the 

 first phalanx. No slip goes to any other digit, as in Wilder's 

 specimen (53). Hepburn (24), Macalister (33), and Humphry (26) 

 found it supplying the medius too. 



The supinato?' brevis is wrapped round a little more than the 

 upper third of the radius. It is musculo-tendinous. 



The extensor ossis metacarpi pollicis and extensor primi inter- 

 nodii pollicis have a common origin from the bones of the forearm. 

 The latter arises from the upper third of the lateral border of the 

 ulna, and the former from the upper two-thirds of the mesial 

 border of the radius. The tendons separate from the combined 

 muscular mass. The broad tendon of the former runs to the 

 trapezium and thumb sesamoid, and the slender tendon of 

 the latter goes to the base of the metacarpal of the thumb. 



The extensor secundi internodii pollicis (extensor pollicis longus) 

 arises from the third fourth of the inner surface of the shaft of 

 the ulna below the extensor primi internodii pollicis and above 

 the extensor indicis. Its long, ribbon-like tendon is inserted 

 into the base of the ungual phalanx of the thumb. Hepburn (24) 

 gives its insertion as the base of the first phalanx, but Humphry 

 (26), Macalister (33), Vrolik (51), Wilder (53), and Wyman (54) 

 recorded conditions as in my specimen. 



Tnterossei : — All authors agree that the dorsal interossei are 

 as in Man, and several have described the six interossei on the 

 palmar surface of the manus. Hepburn (24) has shown that 

 three of the six muscles are the true palmar interossei, namely, 

 those to the ulnar side of the index and the radial sides of the 

 annularis and minimus. The others to the sides of the medius 

 and ulnar side of the annularis are abductors, belonging really to 

 the dorsal series. With his observations I am quite in agreement. 

 The six palmar muscles form a very thick stratum. The con- 

 ditions are shown diagrammatically in text-fig. 35 A. The first 

 dorsal interosseous wraps round the meta,carpal of the index. 

 Taking the deep muscles from within outwards, we find : — 



1. Opponens minimi digiti ; 2. palmar adductor interosseous 

 to the minimus ; 3. palmar abducting interosseous of the annu- 

 laris ; 4. palmar adducting interosseous of the annularis ; 5. pal- 

 mar interosseous deviating the medius to the ulna; 6. palmar 

 interosseous deviating the medius to the radius : 7. palmar ad- 

 ducting interosseous of the index ; 8. pollical head of the first 

 dorsal interosseous covering the metacarpal of the index ; 

 9. deep head of the fiexor brevis pollicis. 



Muscles of the Anterior Abdominal Wcdl. 



The external obliqice arises by well-marked digitations from the 

 outer surfaces and lower borders of ribs 5-11. The mesial 



