262 Transactions. 



the liver at the junction of its lobes. On its way it receives the 

 vesical vein (fig. 2, v.) from the bladder, also two small veins 

 from the skin above the bladder. 



The right parietal vein (fig. 1, p., and fig. 2, p.), coming from 

 the skin as before described, runs in at right angles and joins 

 the anterior abdominal vein about half-way along its course. 



The hepatic portal vein is rather difficult to see owing to it 

 being obscured by the pancreas, through which it runs. It is 

 made up of gastric vein from the stomach, intestinal and spleenic 

 veins from the intestines and spleen respectively. The two 

 latter form the hepatic portal by uniting at the lower end of 

 the pancreas, and after running towards the liver it is joined 

 by the gastric vein. The hepatic portal then runs on and joins 

 with a large branch of the anterior abdominal vein, the ramus 

 descendens,* which runs down from where the anterior ab- 

 dominal vein breaks up into the liver for a short distance 

 between the lobes to meet the hepatic portal. Finally it runs 

 into the liver. 



PART II.— ARTERIAL SYSTEM. 



The arterial system of Hyla aurea corresponds pretty closely 

 to that of Rana, though there are several differences. Unlike the 

 veins, the arteries do not vary much in the different specimens. 



The differences peculiar to the Hyla aurea are as follows : — 



1. The carotid artery, before running to the head, bends 

 back so as to overlap the systemic arch. 



2. The cceliaco-mesenteric arteryf (fig. 4, cm.) comes off 

 from the dorsal aorta almost at right angles, while in Rana it 

 appears to come off at an angle of 45°. 



3. The occipito- vertebral artery (fig. 4, oc.) seems to be very 

 different in its divisions from what it is in Rana. In the Euro- 

 pean frog it divides into two branches soon after it leaves the 

 systemic arch. The occipital branch supplies the back and sides 

 of the head, while the vertebral branch runs clown the back on 

 the dorsal surface of the transverse processes of the vertebrae. 

 In Hyla aurea the occipital branch is much the same as in 

 Rana, but I have so far found no vertebral artery, though I have 

 examined many fresh as well as injected specimens. The ver- 

 tebral artery seems to be replaced in function by several small 

 arteries running from the dorsal aorta and renal arteries. They 

 are short, and supply the muscles, &c, around the vertebral 

 column. 



* " Anatomy of the Frog," Ecker, Eng. trans., 1889, p. 248, fig. 104 (6). 



f" Anatomy of the Frog," Ecker, Eng. trans., 1889, p. 223, fig. 

 143 (?'). " Atlas of Practical Elementary Zootomy," G. B. Howes, 1st ed., 

 pi. iii, fig. xxx (ccb). 



