240 EXCRETION. 



of unstriped muscular fibres interlacing with each, other in 

 every direction. 1 



In addition to the blood-vessels just described, the liver 

 receives venous blood from vessels which have been called 

 accessory portal veins, coming from the gastro-hepatic omen- 

 tum, the surface of the gall-bladder, the diaphragm, and the 

 anterior abdominal walls. These vessels penetrate at dif- 

 ferent portions of the surface of the liver, and may serve as 

 derivatives when the circulation through the portal vein is 

 obstructed. 



Structure of a Lobule of the Liver. Each hepatic lob- 

 ule, bounded and more or less distinctly separated from 

 the others by the interlobular vessels, contains blood-vessels, 

 radicles of the hepatic ducts, and the so-called hepatic cells. 

 The arrangement of the blood-vessels has just been de- 

 scribed; but in all preparations made by artificial injection, 

 the space occupied by the blood-vessels is exaggerated by 

 excessive distention, and the difficulties in the study of the 

 relations of the ducts and the liver-cells are thereby much 

 increased. Under any conditions, there are few questions, 

 if any, in minute anatomy, that are so complicated as that 

 of the origin of the bile-ducts in the lobules. If we were to 

 attempt a critical analysis of the important investigations 

 made upon this subject during the last thirty-five years, we 

 would only illustrate the great diversity of opinion among 

 eminent authors upon difficult anatomical questions. As 

 the important problem in the minute anatomy of the lobules 

 has been the relations of the cells to the radicles of the bile- 

 ducts, we will first take up the structure of the cells. 



Hepatic Cells. If a scraping from the cut surface of a 

 fresh liver be examined with a moderately high magnifying 

 power, the field of view will be found filled with numerous 

 rounded, ovoid, or irregularly polygonal cells, measuring from 

 rsW to TTOT f an mc h m diameter. In their natural con- 



1 SAPPEY, op. cit., p. 300. 



