..LAXI>.< CONNECTED WITH THE INTESTINAL CANAL. 297 



attachments of the liver are found (see peritoneum). The perito- 

 neal covering of the liver is for the most part composed of flattened, 

 ciliated cells (Xeumann and Grunau) ; on the middle lobe these are, 

 however, more or less replaced by non-ciliated cells. The thickness 

 of these cells varies considerably, according to the amount of dis- 

 tension to which the liver is subjected. 



j3. The fibrous covering of the liver is very thin and very diffi- 

 cult to demonstrate ; it consists of connective-tissue fibres with very 

 few corpuscles. This covering is prolonged into the liver along the 

 portal canals, where traces of connective-tissue can always be 

 made out. 



From these processes and from the whole of the inner surface of 

 the general connective-tissue capsule are given off fine trabeculae, 

 in which it is very difficult to find any nuclei ; these trabeculae 

 are everywhere extremely delicate and difficult to demonstrate; 

 nowhere do they form distinct boundaries between lobuli : the 

 structure closely resembles the sustentacular tissue of a lymphatic 

 gland (Eberth). 



y. The blood-vessels to the liver are the portal vessels (p. 

 249), the hepatic veins (p. 247), and the hepatic artery 1 (p. 



2 33)- 



(i) The portal vessels pass into the liver on its ventral surface ; 

 they divide into branches which course along the middle parts of 

 each lobe and give eff smaller branches in all directions towards the 

 periphery ; the interlobular branches (Fig. 1 96 I) forming a very 

 complex capillary network. As compared with the hepatic veins 

 (Fig. 196 II), the interlobular veins do not give off their capillaries 

 so abruptly, but tend to supply these from small lateral branches. 

 The portal veins are accompanied in their course by branches of the 

 hepatic artery, and often by larger bile-ducts, and thus form 

 portal canals. In no part do the portal (interlobular) veins or their 

 branches limit the lobules by distinct rings of vessels, as seen in 

 many higher animals. The interlobular veins and intralobular veins 

 simply interdigitate with each other. 



1 See Plate II, Fig. 196. 



1. Partial injection of the liver from the portal vein (blue) : Rana etcuiemta. G. H. 

 II. Partial injection of the liver from the hepatic rein (red) : Rana ttevlrnta. G. H. 

 ill. Complete injection of the liver from the hepatic artery (red) and from the portal vein 

 (bine) : Rana eteulenta. G. H. 



A Portal (interlobular) veins and their branches. 

 B Hepatic (intralobular) veins and their branches. 

 1 Hepatic arteries and their branches. 



