454 THE DOGFISH CHAP, x 



the ventral end of the first efferent branchial a small 

 mandibular artery (mn) passes to the lower jaw. The dorsal 

 aorta is continued forwards, anteriorly to the first epi- 

 branchial artery, as a slender vessel which soon bifurcates 

 and anastomoses with the dorsal carotid. From the ventral 

 ends of the efferent branchial loops small arteries are given 

 off which supply the lower parts of the head, the branchial 

 region, and the heart (cor). The subclavian arteries (s. cl) 

 arise from the aorta just before it is joined by the last 

 epibranchials. 



In the short-bodied frog we have seen (p. 80) that there 

 is only a single splanchnic or coeliaco-mesenteric artery, 

 which soon divides into a coeliac and a mesenteric. In 

 the dogfish there are four splanchnic arteries, arising 

 separately from, the dorsal aorta, viz., a cceliac, supplying 

 the proximal limb of the stomach and the liver ; an anterior 

 mesenteric, arising a short distance further back and supply- 

 ing the intestine, &c. ; a lienogastric, coming off from the 

 aorta close behind the anterior mesenteric and going to 

 the spleen and part of the stomach and pancreas ; and a 

 small posterior mesenteric supplying the rectal gland. 



As in all Vertebrates, the arteries branch and branch 

 again in the various parts to which they are distributed, 

 their ultimate ramifications opening into a capillary 

 network with which all the tissues except the cartilages 

 and epithelia are permeated. From these systemic 

 capillaries the blood is collected into larger and larger 

 afferent thin-walled trunks or veins, parts of many of 

 which are greatly dilated to form sinuses. 



Most of the blood from the head is brought back by a 

 pair of jugular sinuses (Figs. 119,7'. v > an( ^ I22 > J U S) each 

 of these enters a cardinal sinus (card] , which will be referred 

 to again directly. The blood from the tail is returned by 

 a caudal vein (cd. v, caud) lying immediately beneath 

 the caudal artery in the haemal canal ; this vessel enters 

 the ccelome and then divides into right and left branches, 

 the renal portal veins (r.p.v, r.p), which pass to the 

 kidneys and join with the capillaries of these organs, 

 impure blood brought from the tail mingling with the 

 pure blood of the renal arteries (Fig. 119, r. a). From 



