216 



THE ELASMOBRANCH FISHES 



then inflating the left coronary vein with a blow pipe, whereupon bubbles of 

 air emerge from the left atrial wall into the atrium {Acanthias) . No bubbles, 

 however, appear upon the inflation of the right coronary vein. The same may 



Fig. 199a. Veins of, and in the region of, first dorsal fin, Squalus sucTclii. (L. H. Bennett, 

 orig.) 



c, vein connecting dorsal and lateral cutaneous systems ; c.v., vena circularis ; d.c, dorsal 

 cutaneous vein ; dfv., vein draining dorsal fin. 



])e demonstrated in the coronary arteries but with more difficulty. In Raia 

 evinacea by inflating either right or left vein a similar bubbling occurs from 

 the inner surface of the atrium, although none occurs from the ventricle. In 



the Elasmobranchs, then, the superfi- 

 cial veins of the heart empty into the 

 sinus venosus and the deeper Thebesian 

 vessels enter the atrium direct. 



CUTANEOUS SYSTEM OF VEINS 



The cutaneous veins consist of the dor- 

 sal, ventral, and lateral vessels of the 

 skin. 



The dorsal cutaneous vein collects 

 blood from the skin on the back 

 {Squalus sucklii, fig. 198, p. d.c). It ex- 

 tends along the middorsal line from the 

 caudal fin to the endolymjihatic ducts, 

 and surrounds both dorsal fins in closed 

 loops {c.v., fig. 199a). Posterior to the 

 loop surrounding the first dorsal in 

 Mustelns antarcticus according to T. J. 

 Parker (1886) a median vein passes 

 downward to the left of the column to 

 join the left renal portal. This is essen- 

 tially the condition found in Squalus 

 except that this deep vessel arises as a 



Fig. 199b. Cutaneous veins in region of 

 cloaca, Squalus sucMii. (Edith Stoker, 

 orig.) 



l.a.v., lateral abdominal vein; p.c, post- 

 cloacal segment of ventral cutaneous ; pi., 

 pelvic vein from ventral cutaneous to 

 sinus (s.). 



