DISTRIBUTION OF YESSELS IN GLANDS. 



269 



DISTKIBUTION OF THE YESSELS IN GLANDS. 



[ -12S. Glands in general derive their blood from arteries, 

 and all that is not used for purposes of secretion returns in 

 the usual way through veins and lymphatics into the general 

 current of the circulation. The lymphatics of glands are often 

 very large and conspicuous ; those of the liver are particularly 

 so. Among vertebrate animals the liver receives but a small 

 portion of its blood from an arterial source, and this appears 

 to be exclusively expended upon the gall-bladder, the gall- 

 "ducts, and the coats of the larger vascular trunks, though 

 branches of the hepatic artery can also be followed, entering 

 along with the cellular substance of the organ between its 

 several component lobules. The blood from which the bile is 

 prepared is received from the portal vein, which ramifies 

 through the substance of the liver, and at length anastomoses 

 with the finest subdivisions of the hepatic vein, which spring 

 from the deeper parts, and then flow round about the clusters 

 of hepatic cells united into ccecal-looking lobules (fig. 267). 

 In the two lower classes of vertebrate animals, there is an 

 extension to the kidneys of the same system of circulation 

 which we observe confined to the liver among the two higher 

 classes. In amphibia and fishes a portion of the blood 

 returning from the hind-legs, tail, abdominal parietes, and 

 A B 



\ 



Fig. 278. A couple of feathery lobules from the embryo of the Falco 

 tinnunculus or Hobby, fourteen lines in length ; the substance of the liver 

 is seen composed of large pale granulated particles (cells) ; betwixt the 

 lobules a blood-vessel is seen well filled with blood-discs. 



