THE PANCREAS. 183 



and oblique ones. Outside the muscle lies a dense fibrous coat of fibro-elastic 

 connective tissue. Where invested with peritoneum, the latter is attached 

 to the proper wall of the sac by a layer of fat-laden subserous tissue. 



The cystic and common bile-ducts possess walls that in structure 

 correspond with the hepatic duct above described, consisting of a mucous 

 tunic strengthened by bundles of unstriped muscle. At the lower end of 

 the common bile-duct, the circular fibres are greatly augmented and form a 

 sphincter-like ring around the orifice of the tube where it opens into the 

 duodenal ampulla. The bile, the secretion of the liver, contains no dis- 

 tinctive cells, numerous minute oil drops and granular masses of biliary 

 pigment, with occasional remains of the epithelial cells lining the ducts, 

 being the more common objects encountered when the fresh fluid is exam- 

 ined microscopically. 



The blood-vessels of the liver the functional portal vein, the nutrient 

 hepatic artery and the emergent hepatic veins have been sufficiently de- 

 scribed. It should be noted, however, that the blood conveyed to the organ 

 by the hepatic artery is destined for the nutrition of the interlobular struct- 

 ures, the capsule of Glisson and the walls of the blood-vessels and of the 

 bile-ducts. After supplying these through numerous although small twigs, 

 the blood is collected by venous radicles and emptied either into interlobular 

 branches of the portal vein or into the intralobular capillary network. 



The lymphatics of the liver are represented within the lobules by 

 minute lymph-spaces between the blood-channels and the liver-cells. These 

 spaces drain into the more definite lymphatic paths within the interlobular 

 connective tissue, which as the deep lymphatics surround the blood-vessels 

 and ducts with plexuses that condense into the fifteen or more trunks emerg- 

 ing at the transverse fissure. The superficial lymphatics, very numerous and 

 freely communicating with the deep set, arise from a close-meshed network 

 of lymph-channels within the fibrous capsule. 



The nerves of the liver, from the solar through the hepatic plexus, 

 consist mostly of nonmedullated fibres, very sparingly intermingled with 

 medullated ones. The former are destined chiefly for the walls of the blood- 

 vessels and of the larger ducts, which, after sending filaments to the capsule, 

 they follow within the interlobular tissue, where occasional nerve-cells are 

 found along their course. Some few fibres, possibly secretory in function, 

 penetrate the lobules to end between the liver-cells. The meagre medullated 

 sensory fibres terminate within the interlobular connective tissue. 



THE PANCREAS. 



The pancreas, sometimes called the abdominal salivary gland, is a large 

 tubo-alveolar gland that lies behind the stomach, extending from the loop of 

 the duodenum across the spine and left kidney often as far as the spleen. It 

 is conventionally divided into the head, embraced by the duodenum, the body 

 and the tail. The interlobular connective tissue is unusually abundant; 

 hence the compartments of gland-tissue are loosely united and the entire 

 organ lacks the compactness ordinarily seen in large glands. While agreeing 

 in its general structure with other serous glands, as the parotid, the pancreas 

 differs in certain particulars. The most important of these are: (a) the 

 tubular, rather than saccular, form of the alveoli; (b) the marked differen- 

 tiation of a granular zone in the cytoplasm of the secreting cells; (c) the 

 absence of specialized intralobular ducts; and (</) the presence of the char- 

 acteristic islands of Langerhans. 



