THE LEVER. 119 



impinge directly upon the columns of the network of hepatic 

 cells, as the diagram in fig. 221 shows, so that their cavity is 

 terminated by hepatic cells : and, judging from the scantiness 

 of the finest branches of the hepatic duct, I believe that such 

 communications exist, in no very great numbers, at the circum- 

 ference of the hepatic islets. 



Whatever view we may take of the connexion of the hepatic 

 cell-networks with the efferent biliary canals, it is undeniable 

 that any such connexion only takes place upon the surface of 

 the hepatic islets and not in their interior and that, therefore, 

 the bile which is formed here, must be transmitted outwards 

 from cell to cell. Such a process of transmission through 

 closed cells, involves, as vegetable physiology teaches us, no 

 impossibilities ; but it can hardly take place so rapidly as in 

 those localities where actual canals subserve this purpose. 

 Since the bile, as late investigations tend to show with in- 

 creasing clearness, is not only excreted from the blood, but 

 absolutely formed in the liver and is at the same time by far 

 the most complicated of all the secretions, it may be presumed 

 that the peculiar arrangement of the secreting parenchyma in 

 the liver stands in relation with these peculiarities. In fact, 

 the plasma of the blood, in passing through many cells and 

 being subjected to the metabolic influence of each before it 

 reaches the efferent duct, must undergo very different changes 

 from those which it suffers when it is separated from the 

 glandular canals only by a single layer of cells and one or 

 two structureless membranes. The resulting necessary slow- 

 ness of the secretion is compensated by the size of the organ 

 and the elaboration of the product. 



[If nitric acid be added to the hepatic cells, they assume a 

 greenish yellow colour, as was originally stated by Backer. 

 Sugar and sulphuric acid turn them red ; water produces an 

 abundant precipitate of dark granules in the cells, which are 

 usually, readily and completely soluble in acetic acid, so that 

 they become more or less pale, often to a considerable extent ; 

 the same thing occurs if the acid be added directly. If the 

 liver be boiled, its parenchyma becomes hard and the cells 

 acquire a concentrated and wrinkled appearance. Dilute 

 caustic alkalies rapidly attack the hepatic cells in animals, and 



