BY W. J. S. >[cKAY. 329 



condyle it becomes rapidly narrower, and its anterior border is 

 now joined by a thick belly of muscle (the scapular portion of the 

 latissimus) which arises fioni the posterior extremity of the verte- 

 bral border of the scapula. (Fig. 10, Lt. D.S.) The conjoined 

 muscles continue on and are inserted by a well-marked flattened 

 tendon on the posterior border of the inner part of the internal 

 condyle ; the median, ulnar, and deep radial nerves winding from 

 witliin outwards over the dorsal face of tlie tendon. (Fig. 10, 

 Lt. D.A.) 



Relations. At its origin the posterior dorsal portion is 

 intimately related to the origins of the posterior part of the 

 trcipezius, the dermo-dorsi cervicalis, and sacro-lumbalis. The 

 anterior portion is likewise intimately related to the origin of the 

 trapezius from the vertebrae. The scapular slip is closely connected 

 at its origin with the origin of the teres major and insertion of 

 the costal serratus. Both the anterior and posterior dorsal por- 

 tions are triangular in outline, the anterior and posterior borders 

 of the latter being very thin, and while the posterior border of the 

 former is also thin, the anterior border is (piite 1 cm. thick where 

 the scapular slip joins it. 



Orsithorhynchus. 



Origin, (a) Vertebral portion. — This muscle arises from the 

 spines of the lst-9th dorsal vertebra inclusive ; the origin being- 

 fleshy from the lst-6th inclusive, ])ut l^y aponeurosis from the Gth- 

 9th spine. (Fig, 12, Lt. D.A.) 



(b) Costal portion. — This arises by fleshy bundles from the 4th 

 12th rib inclusive. The fasciculus attached to the 12th rib is 

 about 2-5 cm. from the mid-dorsal line, while each fasciculus 

 anterior to this gradually approaches nearer to the median line. 

 The costal bands run forward and outwards, coalescing to form a 

 broad triangular sheet of muscle, (Fig. 12, Lt. D.P.) 



Insertion. The portion of the latissimus arising from the 

 spines of the vertebrae forms a triangular superficial muscle, which 

 hides from view the antero-internal portion of the muscle formed 

 by tlie coalescence of the costal fasciculi. As the vertebral and 



