CHAP. XIV.] ALIMENTATION. 



these fine canaliculi pass into the interlobular bile ducts which, 

 running in connection with the blood-vessels, finally empty into 

 the two bile ducts which leave the liver at the opening, spoken 

 of above as the " gate of the liver." 



The cells of the liver manufacture bile from the blood, and 

 discharge this into the minute bile canaliculi, whence it passes 

 into the bile ducts to be conveyed into the small intestine. 

 The cells, however, perform another important function, in that 

 they change some of the substances brought to them in the 

 blood from the digestive organs in such a manner as to render 

 these substances suitable for the nutrition of the body ; but, at 

 present it will be enough to consider the secretion of bile as 

 the only function of the liver. 



The bile is taken from the liver by a right and left duct, 

 which soon unite to form the hepatic duct. The hepatic duct 

 runs downward and to the right for an inch and a half, and 

 then joins at an acute angle the duct from the gall-bladder, 

 termed the cystic duct. The hepatic and cystic ducts together 

 form the common bile duct (ductus communis choledochus), 

 which runs downwards for about three inches, and enters the 

 duodenum at the same opening as the pancreatic duct. 



The gall-bladder (vide Fig. 102) is a pear-shaped sac, lodged 

 in a depression on the under surface of the right lobe of the 

 liver. It is lined by columnar epithelium, and its walls are 

 formed of fibrous and muscular tissue. It is held in position 

 by the peritoneum, and serves as a reservoir for the bile. Dur- 

 ing digestion the bile is poured steadily into the intestine ; in 

 the intervals it is stored in the gall-bladder. 



To recapitulate : the digestive apparatus may be said to con- 

 sist of a tube and of important accessory organs placed in close 

 connection and communication with it. For convenience of 

 description, the tube may be divided in sections, each of which 

 is furnished with mechanical and chemical appliances for reduc- 

 ing the food into a soluble condition. First, the mouth cavity, 

 which is provided with muscular cheeks and movable jaw, 

 tongue, teeth, and the chemical solvent, saliva, secreted by the 

 salivary glands ; secondly, the two passages, the pharynx and 

 oesophagus, serving to convey the food into the next section, 

 the stomach, which is furnished with muscular walls for crush- 

 ing and churning the food, and with glands to secrete the acid 



