THE DIGESTIVE SYSTEM 



299 



cells— cells of Kupjfcr — within the lobule. These are interpreted 

 by Kupffer as belonging to the endothelium of the intralobular 

 capillaries. 



Comparing the liver with other compound tubular glands, it is 

 seen to present certain marked peculiarities which distinguish it and 

 which make its structure as a compound tubular gland difficult to 

 understand. The most important of these are the following: 



d 

 Fig. 204. Fig. 205. 



Fig. 204. — Scheme of an Ordinary Compound Tubular Gland. In lobule 3 only the 

 ramifications of the excretory duct, without endpieces, are shown. (Stohr.) a, 

 Branches of excretory duct; b, artery; c, vein; d, terminal tubules; c, capillaries. 



Fig. 205. — Scheme of Liver. In lobule i, onl}' the direction of the endpieces is shown; 

 in'lobule 2 only their branching; in 3 only the excretory ducts. (Stohr.) a, Branches of 

 excretory duct; b, portal vein; c, terminal tubules (hepatic cords); d, capillaries; e, vein 

 (central and sublobular). 



The extremely small amount of connective tissue. In the human 

 liver there is not enough interlobular connective tissue to outHne the 

 lobules, while intralobular connective tissue demonstrable by ordi- 

 nary staining methods is wholly absent. There is thus no connective 

 tissue seen separating the cells of one tubule from those of another 

 as, for example, in such a gland as the submaxillary. (Compare Figs. 

 186 and 197.) The result is that cells of neighboring tubules lie side 

 by side, and back to back as it were, with no intervening connective 

 tissue. 



The fact that unlike the tubules of other glands, the liver tubule con- 



