320 SPECIAL ANATOMY. 



Artt. interossece metacarpi dorsales. These are larger or smaller, going 

 along to the inferior extremity of spaces between the metacarp. 

 bones, or to the articulations of the first and second phalanx, pass 

 with branches of arcus volar. sublimis, and assist in forming art. digi- 

 tales. 



2. Arcus volaris profundus, lies close upon the palmar surface of the basis 

 ossium metacarpi, covered by the nerves, tendons, and muscles of the palm of 

 the hand, below slightly convex; principally formed of the transversely pass- 

 ing terminations of art. radialis ; gives off: 



a. Eami ascendentes, very short branches for the carpus, which anastomos- 

 ing with branches of radialis and ulnaris (and interossea) form the rete 

 carpeum volar e. 



b. Kami descendentes s. interossece volares, three to four; they pass in the 

 second to the fourth spatium inteross. metacarpi, at the inferior extremi- 

 ties of which they anastomose with the branches of arcus volare sublimis. 

 The first and largest at the radial border of the index finger is often 

 wanting. 



c. Eami perforantes, three, pass at the superior extremities of the second to 

 the fourth spat, inteross. metacarpi, from before backwards to the rr. de- 

 scendent. art. radialis, and form with these the small interossece dorsales. 

 (See arcus dorsalis.) 



3. Arcus volaris sublimis, lies in the palm of the hand, covered by aponeu- 

 rosis palmaris, upon the tendons of flexorr. digitor., below convex; rather 

 nearer to the carpal articulation than the deep arch ; chiefly formed of ram. 

 sublimis art. ulnaris. From the convexity arise : 



Art. digitales, three, which pass between the tendons of the flexors of 

 the fingers to the heads of the ossa metacarpi, in the second to the fourth 

 interspaces, there anastomosing with the interossea dorsales ; they bifur- 

 cate, and thus supply the radial border of the five fingers, and the ulnar 

 border as far as the second finger. On the anterior surface of the pha- 

 langes, lying close to the flexor tendwns, they send branches to the dorsal 

 surface, which, like these, but smaller, pass to anastomose with each 

 other by means of transverse branches, and give branches to the skin. 

 The radial border of the index finger and thumb is supplied by ram. volaris 

 art. radialis, which anastomoses with the arcus volaris sublimis. 



Aorta descendens, the descending aorta. 



570. A. Aorta descendens thoracica, the thoracic aorta. 



Position : on the left side of the twelfth [eighth inferior] dorsal 

 vertebra, seven to eight inches long, before the vertebral column 

 (above separated by duct, thoracic.) ; behind the left pulmonary 

 vessels (above), the oesophagus (below), and the pericardium (in 

 the centre) ; has to the left the mediastinum, to the right the osso- 



