1904.] CIRCULATORY SYSTEM IN THE OPHIDIA. 363 



of vertebrse is supplied by each intercostal and its supei'ficial 

 continuations ; thus I counted from the beginning of the series 

 7, 7, 5, 3, 6, 3, 3 vertebrse belonging to the area of each inter- 

 costal. In one or two cases it is noteworthy that the superficially 

 running portion of an intercostal did not fork either anteriorly or, 

 it may be, posteriorly to supply both sides of a vertebra ; in such 

 cases one side was supplied by the end of one intercostal and the 

 other side by the anterior end of the next intercostal. Immediately 

 after the livei' is a stretch of nine vertebras served by branches 

 of a continuous superficial vertebral which has two intercostal 

 affluents. The rest of the body is supplied by more numerous 

 intercostals, which generally serve only two successive vei'tebi-se 

 and often only one vertebra. 



Visceral branches of the Common Aorta. — In the region of the 

 liver a regular series of trunks is given ofi" which supply that 

 organ and the oesophagus. They are closely associated with 

 branches of the portal vein which bring blood from the oesophagus 

 to the liver, so closely that it will be convenient to consider the 

 vessels together. Although the association between the portal 

 vessels and the branches of tTie aorta is close, there is not an exact 

 correspondence. The first hepatic branch of the aorta is situated 

 about 2 inches behind the anterior end of the liver. It runs 

 straight to the liver, and just before reaching it divides into an 

 anteriorly and posteriorly running branch. The former reaches 

 nearly to the tip of the liver, and takes the place of the two 

 missing hepatic branches of the aorta. About halfway between 

 its origin and its bifurcation a branch is given ofi" to the 

 oesophagus, from which arises immediately a slender twig to 

 the walls of the lung. The portal branch which accompanies it 

 accompanies it closely ; its main trunk is derived from the 

 oesophagus, and this lies in contact with the oesophageal branch 

 of the aorta. There is also a branch from the lung- walls also 

 lying close to the lung-branch of the aorta, while the main 

 hepatic stem is accompanied by a portal branch which appears to 

 arise partly from the lung- walls and partly from the walls of the 

 aorta. In front of this first hepatic trunk are two portal vessels 

 arranged at regular intervals, which appear to be serially con- 

 tinuous with the poi'tal branch already described. They are 

 not, however, collecting trunks from the oesophagus, and will be 

 described elsewhere. The next hepatic branch of the aorta arises 

 about an inch further on ; it is accompanied by a portal branch 

 which, like the two last-mentioned, mainly collects blood from the 

 body- walls. This second hepatic artery divides into two much 

 earlier than does the first of this series of vessels. There are 

 altogether 8 of the hepato-oesophageal branches of the aorta whicli 

 arise at rather irregular intervals and have no relation in position 

 or number to the underlying intercostal arteries. Between the 

 first two hepatic branches there is an unusually wide interval, 

 almost suggesting a missing artery. So far as concerns its 

 oesophageal branch this arteiy is represented by a long descending 



