DIGESTIVE SYSTEM 



133 



microscopic research reveals fine distinctions which are not to 

 be ignored. Thus, the hepatic lobes are: 



In man . . ri to 23 mm. long 



'8 i'5 ,, broad 

 In the pig . . 1-5 2-5 long 



i 1-5 broad 1 



Oppel - also mentions the similarity between the human liver 

 and that of the pig, but draws attention also to its resemblance 

 to that of the dog. 



He regards as the distinctive characters of the human liver 

 (see Fig. 72) the frequent union of the lobes to double and 

 three-fold formations ; further, the circumstance that the 



FIG. 73. A portion of the liver. (Thome, Zoologie.) 

 i, artery; 2, portal vein ; 3, bile duct. 



FIG. 74. Liver cells. 

 (Haeckel, An- 

 thropogenic.) 



majority of the intralobular biliary ducts are situated in the 

 marginal surface of the hepatic cells, though, between the mar- 

 gins, biliary ducts also occur on which border three or four 

 hepatic cells. 



The average diameter of the human hepatic cell (see Fig. 

 74), which frequently shows two distinct nuclei, is from 18 to 

 26 m., the lobes measuring i mm. crosswise and i'5 to 2 mm. 

 lengthwise. 



The first appearance of a pancreas among the invertebrates 

 is in the molluscs (Gastropoda and Cephalopoda), either in 

 the form of gland lobules attached to the excretory ducts of 

 the hepatic lobes, or in that of a pouch provided with a folded 



1 Ellenberger, loc. cit., p. 710. 2 A. Oppel, loc. cit., part iii., p. 1067. 



