NERVES AND LYMPHATICS OF THE LIVER. 399 



the bile, even in living animals. It is marked by a large number of minute 

 excavations and is covered with cells of columnar epithelium. This mem- 

 brane contains a large number of mucous glands. 



The gall-bladder is an ovoid or pear-shaped sac, about four inches (10 

 centimetres) in length, one inch (25 mm.) in breadth at its widest portion, 

 and capable of holding an ounce to an ounce and a half (30 to 45 c. c.) of 

 fluid. Its f undus is covered entirely with peritoneum, but this membrane 

 passes only over the lower surface of its body. 



The proper coat of the gall-bladder is composed of ordinary fibrous tissue 

 with a few elastic fibres. In some of the lower animals there is a distinct 

 muscular coat, but a few scattered fibres only are found in the human sub- 

 ject. The mucous coat is of a yellowish color, with verysmall, interlacing 

 folds which are very vascular. The mucous membrane of the gall-bladder 

 has a general lining of columnar epithelium with a few goblet-cells. In the 

 gall-bladder are found small, racemose glands, formed of four to eight folli- 

 cles lodged in the submucous structure. These are essentially the same as 

 the glands opening into the ducts in the substance of the liver, and they 

 secrete a mucus which is mixed with the bile. 



Nerves and Lymphatics of the Liver. The nerves of the liver are derived 

 from the pneumogastric, the phrenic, and the solar plexus of the sympathetic. 

 The branches of the left pneumogastric penetrate with the portal vein, while 

 the branches from the right pneumogastric, the phrenic and the sympathetic, 

 surround the hepatic artery and the hepatic duct. All of these nerves pene- 

 trate at the transverse fissure and follow the blood-vessels in their distribu- 

 tion. They have not been traced farther than the final ramifications of the 

 capsule of Glisson, and their exact mode of termination is unknown. 



The lymphatics of the liver are very abundant. They are divided into 

 two layers ; the superficial layer, situated just beneath the serous membrane, 

 and the deep layer. The superficial lymphatics from the under surface of 

 the liver, and that portion of the deep lymphatics which follows the hepatic 

 veins out of the liver, pass through the diaphragm and are connected with 

 the thoracic glands. Some of the lymphatics from the superior, or convex 

 surface join the deep vessels that emerge at the transverse fissure and pass 

 into glands below the diaphragm, while others pass into the thoracic cavity. 



The mode of origin of the lymphatics is peculiar. The superficial lym- 

 phatics are subperitoneal and are connected with spaces or canals in the 

 general connective tissue of the liver. The deep lymphatics are supposed to 

 originate by perivascular canals surrounding the blood-vessels of the lobules, 

 which are connected with vessels in the walls of small branches of the hepatic 

 and portal veins, afterward surrounding the larger vessels. 



Mechanism of the Secretion and Discharge of Bile. In its anatomy the 

 liver differs greatly from other glandular organs, both secretory and excretory. 

 The liver-cells are not enclosed in ducts, but are surrounded by a plexus of 

 exceedingly small vessels which undoubtedly receive the bile as it is formed. 

 The liver, also, is supplied with both venous and arterial blood, the venous 

 blood largely predominating. In addition it is now recognized that the bile 



