DIGESTION 239 



and the central one the smallest. There is, in addition, a small lobule, named 

 the lobulus Spigelii, connected with the posterior face of the right lobe. 



The structure of the liver is highly complex, but it consists essentially 

 of a mass of cells separated by connective tissue into small lobules, which 

 are further defined and isolated by the blood-vessels and bile-ducts which 

 surround them. 



The cells. — These are rounded masses of protoplasm without cell 

 membrane, but containing a nucleus and granules of various kinds, some 



The Liver and Pancreas 



1 Right lobe. - Middle lobe. :i Left lobe. 4 Lobulus Spigelii. •"' l:ight lateral ligament. '' Left lateral 

 ligament 7 CKsophagus. * Posterior vena cava. 10 Ductus choledochus or bile-duct. "Pancreatic 

 duct. '- Duodenum, or first portion of small intestine. B, Pancreas. 



being particles of pigment, others oil globules, and others again grains of 

 glycogen. They are separated from one another by minute blood-vessels, 

 by the capillary bile-ducts, and by lymph spaces. Their functions are to 

 secrete bile, to store up glycogen, and to give that substance up again to 

 the blood when required for the purposes of the economy. 



The blood-vessels. — Three blood-vessels are concerned in the circu- 

 lation of the liver. Two carry blood to it — the hepatic artery and the 

 portal vein — while the third, the hepatic vein, returns the blood which 

 has circulated through the gland to the posterior vena cava, which it 

 joins just before that vessel perforates the diaphragm to discharge its 

 blood into the right auricle of the heart. The hepatic artery divides and 

 subdivides to form capillaries which join those of the portal vein in the 

 lobules. The portal vein is a large trunk that contains the blood returning 

 from the stomach and intestines, and from the spleen and pancreas. Hav- 

 ing reached the inferior surface of the liver it penetrates into its substance, 



