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. Cceliaco-Afcsciilcric Artery. 



The CLvliaco-mcscnteric artery (PL I, figs, i and 5 ; Coe- 

 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 a rather short vessel. With the 

 subclavian it has its source in the common chamber (PL 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 coeliac and mesenteric 

 trunks. 



{a) Coeliac Artery (PL I, figs, i, 6 and 11 ; Coe.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 ca^ca, 

 and a part of the posterior end of the intestine. 



The first branch to be given off from the coeliac is the left 

 hematic artery (PL I, figs. 6 and 11; L.Hep.A.). It leaves 

 the coeliac 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 posterior g'all- 

 bladder arte?'y (P\. 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 (3) of the left portal vein 



Proc. Wash. Acad. Sci., June, 1905. 



