110 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



lining and the remainder of its structure is chiefly fibrous. A 

 little plain muscular tissue may exist. Its capacity is about one 

 and a half ounces. Mucous glands are found in its lining, as in 

 that of the large ducts, and these are responsible for the mucin 

 of the bile. 



Hepatic Nerves. With regard to the exact destination of 

 the nerves entering the liver, little is known. Evidence going 

 to establish the termination of fibers in the cells, that is, the 

 existence of distinct secretory fibers, is meager. There is little 

 doubt that secretory fibers for the glycogenic function of the 

 liver do exist. It is known that fibers from the vagus, phrenic 

 and solar plexus enter the fissure, but they cannot be followed 

 farther than the ramifications of Glisson's capsule between the 

 lobules. Of course, vaso-motor fibers go to the vessels, as else- 

 where. Fibers acting similarly go also to the muscular tissue of 

 the large ducts and of the gall bladder. The contraction of the 

 gall bladder is thought to be reflex, afferent impressions being 

 conveyed by the vagus from the mucous membrane of the 

 duodenum. 



Hepatic Lymphatics. The lymphatics are abundant, and 

 those not originating in the connective tissue are thought to 

 originate by perivascular canals surrounding the blood-vessels 

 of the lobules. The fact that when the outflow of bile is occluded 

 it passes, not into the vascular, but into the lymphatic circulation 

 is a curious circumstance. It may be due to the absence of a 

 definite wall for the intralobular ducts and their comparatively 

 free communication with the lymphatics in those localities. 



Properties and Composition of Bile. Human bile is of a 

 dark greenish-red color, has a bitter taste and is practically odor- 

 less when fresh. It undergoes putrefaction easily, but is not 

 coagulable by heat. It is viscid, chiefly on account of the mucin 

 it contains. It has an alkaline reaction, and a specific gravity 

 of about 1030. Besides water, which constitutes more than 

 ninety per cent, of its bulk, it contains the sodium salts of tauro- 



