THE ELASMOBRANCII FISHES 



167 



brandies from the ventral gastric artery. It then extends to the cardiac 

 stomacli wliere it anastomoses with the anterior gastrosplenic artery which 

 sup})lies a more anterior segment of the stomach. 



The ventral intestinal artery (v.i.a.) passes over the distal end of the py- 

 lorus and the ventral lobe of the pancreas, to appear on the ventral side of the 

 valvular intestine. On the intestine it supplies the distal part of the duodenum 

 and furnishes the ventral side of the valvu- 

 lar intestine with numerous paired annular 

 branches which run on the attached edge of 

 the spiral valve more or less nearly encir- 

 cling the intestine (see fig. 155). 



The gastroduodenal artery {gd., fig. 156) 

 in addition to supplying the proximal part 

 of the duodenum sends a short branch to the 

 tip of the pylorus. 



SUPEEIOE (ANTERIOR) MESENTERIC AND 

 ITS BRANCHES 



The superior mesenteric artery (s.m., fig. 

 157) as such is usually absent in Heptanchus 

 moculatus and when present it is never more 

 than a short stem given off from the dorsal 

 aorta a little more than one-half the way 

 back in the body cavity. (In figure 155 the 

 superior mesenteric branches [a.gps. and 

 p.i.a.] have been displaced forward.) It im- 

 mediately divides into: (1) an anterior gas- 

 tro-pancreaticosplenic {a.gps., fig. 155) and 

 (2) a posterior intestinal (p.i.a.). 



The anterior gastro-pancreaticosplenic 

 (a.gps.) sends branches to the dorsal and distal parts of the cardiac stomach, 

 to the dorsal lobes of the pancreas, and to the spleen in and on the angle of the 

 stomach. 



The posterior intestinal artery runs back over the mesentery to the valvular 

 intestine which it joins at about the middle of its length. Then, as the dorsal 

 intestinal (d.i.a.), the artery continues backward to supply the dorsal poste- 

 rior half of the spiral valve with annular branches. Some of these branches 

 anastomose with similar annular branches from the ventral intestinal artery. 

 Finally the dorsal intestinal artery traverses the region of the colon and ter- 

 minates in the rectal gland where it joins branches of the inferior mesenteric. 



Fig. 156. Arterial supply to the du- 

 odenum. Dorsal view, Keptanclius 

 maculatus. (Marie Weldt, orig.) 



a. La., anterior intestinal artery; 

 du., duodenum; gd., gastroduodenal 

 artery; i.a., intraintestinal artery; 

 pn., pancreatic branch ; pn.^'", dor- 

 sal and ventral lobes of pancreas; 

 p.gps., posterior gastro-pancreatico- 

 splenic artery ; py.a., pyloric artery ; 

 v.i.a., ventral intestinal artery. 



INFERIOR (POSTERIOR) MESENTERIC ARTERY 



The inferior mesenteric artery (i.m., figs. 157 and 155) arises as a single trunk 

 a few segments behind the superior mesenteric region. It runs along the an- 

 terior margin of the mesorectal mesentery to the anterior part of the rectal 



