1904.] CIRCULATORY SYSTEM IX THE OPHIDIA. 343 



body- wall to one side or the other of the dorsal median line ; but 

 there is no regularity in this arrangement — there is, for instance, 

 no regular alternation from right to left. The first 9 inter- 

 costals enter the body- wall to the left of the dorsal middle line ; 

 the tenth to the fourteenth (inclusive) perforate the parietes on 

 the right side ; the fifteenth, sixteenth, and seventeenth revert 

 to the left side. The accessory portal veins are nine in number. 

 As a rule, they accompany somewhat closely the intercostal 

 arteries. The fii'st of them thus accompanies the second inter- 

 costal, but before entering the liver it is joined by a branch from 

 the body- wall which lies midway between the second and third 

 intercostals. The remaining vessels are close to their respective 

 intercostals, except the 6th vein, which lies between the fifth and 

 sixth arteries, and the ninth, which has a corresponding position 

 further on. As is the case with the intercostal arteries, the 

 intercostal portal veins are irregular in their origin from the right 

 or left of the mid-dorsal line. 



All those, however, which are accessory portals, opening directly 

 into the liver, arise on the left side, as do the four following 

 intercostal afiluents of the portal vein. The fourteenth vessel of 

 the whole series is on the right side. This vessel, moreover, 

 appears to be the last of the parietal portal system. It lies well 

 in front of the origin of the mesenteric — in fact, a little behind 

 the commencement of the narrow pyloric region of the stomach. 



The anterior vertebral artery becomes lost in the parietes 

 4 inches beyond the heart and 4 inches from the tip of the snout. 

 It gives off 7 intercostals at not regular intervals ; these are 

 accurately median in position. 



The artery of the fat-body receives from the aorta only one 

 important aifluent which belongs almost entirely to itself. This 

 artery arises from the aorta between the two testes, and, after 

 giving off a very slender twig to the vas deferens of the anterior 

 testes, supplies the fat-body. Anterior branches of the gastric 

 artery supply the fat-body. 



This Snake has an unusually extensive system of gastric arteries. 

 I counted 15 of themi altogether. The first artery supplies one 

 side of the stomach and the second the opposite side. The 

 remaining arteries show with some irregularity the same alter- 

 nation. The tenth gastric artery sends off two slender twigs 

 backwards for the supply of the pancreas and adjacent viscera. 

 It also gives off a backwardly running branch which joins the 

 gastric branch of the superior mesenteric and also divides into 

 two trunks, one for each side of the stomach. 



The next artery for the supply of the viscera which arises 

 after the gastric is the superior mesenteric. This artery has the 

 usual two branches ; but before it divides into these it gives off a 

 slender forwardly running branch to the pancreas ti.nd spleen. 

 This branch runs to the left of the portal vein, while the gastric 

 branch runs to the i-ight of the same vein. 



The spermatic and renal arteries have no definite relations to 



