1020 MR. L. R. CRAWSHAY ON THE ARTERIAL [DeC. 11 



The arrangement was rather different in the two species of Bufo, 

 but in all the six species of Rana it may be said that the 

 independence of these three branches and their association 

 respectively with the proximal, median, and distal portions of 

 the intestine was distinctly marked. For purj)oses of comparison 

 I will therefore refer to them as the proximal, median, and distal 

 rami. 



The proximal ramtts soon divides in the mesentery near the 

 end of the first loop of the intestine. A large branch is then 

 given off which soon attaches itself to the surface of the gut, 

 running along the duodenum to the pylorus, Avhere it generally 

 anastomoses with the distal portion of the A. gastrica dextra. As 

 previously mentioned, in H.catesbiana it took up the whole function 

 of that artery, running for a considerable way up the right side of 

 the stomach (text-fig. 146, p. 1017). R.tigrina and one specimen 

 of R. clamata were the only examples in which no such anastomosis 

 was observed. In Bufo imauritanicus a small vessel was giA^en off 

 at the bile-duct {A . pancreatica postei'ior, Gaupp) and ran a con- 

 siderable way along it, supplying the pancreas, &,c. This vessel 

 was also present in one specimen of R. temporaria, and may have 

 escaped my notice in other individuals, though I did not observe it. 

 The other portion of this branch of the mesenterica anterior 

 runs backwards, and normally, unlike the duodenal portion, shortly 

 breaks up in the mesentery into a variable number of vessels 

 which mostly further subdivide, confining themselves I'oughly 

 to the first half of the small intestine. Such was the case in 

 R. temporaria, clamata, tigrina, cateshiana, and hexadactyla. In 

 R. escidenta, instead of division in the mesenteiy, a single vessel 

 ran along the wall of the intestine like the duodenal portion. 

 Bufo horeas was the same as R. escidenta. In B. mauritanicus 

 the intestinal portion took ofi" from the main trvmk quite 

 independently of the duodenal portion of this ramus and more 

 distally. 



The median ramus runs for some distance unbroken and then 

 ■divides and subdivides rapidly in the mesentery into a number 

 of vessels, which are distributed roughly to the distal half of the 

 small intestine. The variation to which this branch is liable 

 among individuals of a species seems to be too great to admit of 

 comparison being drawn between the species themselves. 



The distal ramus [rr. hcemorrJioidales anteriores, Gavipp) is, as a 

 rule, almost confined in its distribution to the large intestine. 

 R. tigrina was exceptional in that about one-third of it went to 

 the small intestine. More often its first vessel reaches the gut 

 nearly on the border line between these two regions. Its 

 independence as a distinct unit of the mesenteric system was 

 clearly shoAvn in all the species except in B. horeas, where it was 

 more difficult to difierentiate it from the median ramus. In 

 R. tigrina it was very much broken up in its course through the 

 mesentery. In R. escidenta it reached the intestine as a single 

 vessel only. Posteiiorly, it usually runs back in close contact 



