The Digestion of Food 



171. The Hepatic Lobules. When a small piece of the 

 liver is examined under a microscope it is found to be 

 made up of masses of many-sided minute bodies, each 

 about T ^Yo ^ an ^ nch m diameter, called hepatic or liver 

 cells. The active work of the liver is done in the hepatic 

 cells. 



Each group of cells is called a lobule, and they give to 

 the liver its coarse granular appearance when torn across. 

 Each lobule is attached to a branch of the hepatic vein, 

 the large vein which carries the blood away from the 

 liver. The lobules are polyhedral in shape, with their 

 cells arranged in rows, radiating from the center to the cir- 

 cumference. Minute channels separate the cells one from 

 another and unite in a main duct leading from the lobule. 

 ' 172. The Portal Vein. There 

 is a large vessel, called the por- 

 tal vein, which during digestion 

 brings to the liver blood heav- 

 ily laden with the products of 

 .digestion, absorbed from the 

 stomach and intestines. On en- 

 tering the liver this great vek*= 

 conducts itself as if it were 

 an artery. It divides and sub- 

 divides into smaller and smaller 

 branches, until it ends in a net- 

 work of capillaries within that 

 organ. 



A- 173. ~The Bile. 

 the 



FIG. 57. Tubular Glands of 

 the Small Intestines. 



A, B, tubular glands seen in verti- 

 cal section with their orifices at C 

 opening upon the membrane be- 

 tween the villi ; D, villus. (Mag- 

 nified 40 diameters.) 



We have in 



liver, on a grand scale, 

 exactly the same conditions that obtain in the smaller and 

 simpler glands. The thin-walled liver cells take from the 

 blood brought to them by the portal vein certain materials 



