BLOOD-VASCULAR SYSTEM OF THE LORICATI . 65 
through the scapula foramen with the external subclavian vein 
and a branch of the first and second spinal nerves, and then 
runs obliquely ventrad between the superficial and profundus 
abductor muscles, giving off several branches to each. 
6. Caliaco-Mesenteric Artery. 
The celiaco-mesenteric artery (Pl. I, figs. 1 and 5; Ce- 
Mes.A.), which is destined to supply the entire viscera 
with the exception of the kidney, urinary-bladder, and repro- 
ductive organs, is in itself arather short vessel. With the 
subclavian it has its source in the common chamber (PI. I, 
fig. 5; C.C.) beneath and to the right of the aorta and sub- 
clavians. It pursues a ventro-caudal course, and passing 
between the inner side of the right fork of the kidney and the 
right dorsal branchial retractor muscle enters the thoracic 
cavity, where it soon divides into the cceliac and mesenteric 
trunks. 
(a) Celiac Artery (P\. I, figs. 1,6 and 11; Co.A.).— This 
large vessel for a short distance, runs parallel, but cephalad to 
the mesenteric artery, then curving around under the stomach, 
supplies the liver, ventral part of the stomach, pyloric ceca, 
and a part of the posterior end of the intestine. 
The first branch to be given off from the ceeliac is the left 
hepauc artery (Pi. 1, figs. 6 and 115 \L.Hep.A.). It leaves 
the cceliac under the stomach and breaks up into as many 
branches as there are terminal branches of the left portal vein. 
These branches are somewhat irregular, but the first and most 
cephalic one accompanies terminal branch (a) of the left portal 
vein. Usually this branch is the source of the posterzor gall- 
bladder artery (Pl. I, fig. 11; P.G.Bl.A.), which runs along 
the dorsal surface of the gall-bladder and anastomoses with the 
anterior gall-bladder artery, which is a branch of the right 
hepatic artery (a branch of the mesenteric artery). Both gall- 
bladder arteries break up into a minute capillary system on the 
surface of the gall-bladder. A minor posterior gall-bladder 
artery is often given off to the ventral surface of the gall- 
bladder (see fig. 11). The second branch of the left hepatic 
artery accompanies terminal branch (6) of the left portal vein 
Proc. Wash. Acad. Sci., June, 1905. 
