74 PRACTICAL HISTOLOGY. 



with a distinct radial arrangement near the hepatic vein, though the meshwork becomes 

 more polygonal at its outer part. Relatively the hepatic cells appear smaller than in the un- 

 injected specimen. Sections of the hepatic vein issuing from within a lobule ought to be 

 looked for. A double injection is, of course, very instructive, though the areas of the respec- 

 tive veins may not be accurately mapped out. (Indicate the general arrangement of the blood- 

 vessels in PI. XVI., Fig. i.) 



Opaque Injections. It is well to examine by reflected light a section of a liver whose 

 blood-vessels have been injected by an opaque mass say red in the hepatic vein, and yellow 

 in the portal. 



BILE-DUCTS. 



PREPARATION. Inject the fresh and still warm liver of a rabbit or guinea-pig (killed 

 by bleeding) from the bile-duct with a cold, watery, fresh-filtered solution of Prussian blue 

 (p. li). This is by no means an easy task. The great thing is to use a constant and not 

 too great pressure (p. liii). Whenever the outer part of the lobules begins to get blue, stop. 

 It is advantageous to inject a red gelatine mass into the portal vein after the injection of 

 the bile-ducts has been completed. Place the liver in alcohol for a few hours, then cut it into 

 pieces, and put some in alcohol and others in Muller's fluid for two weeks. Make sections in 

 the usual way by freezing. 



EXAMINATION (L). In a section of a piece hardened in alcohol and mounted in dammar 

 observe the larger interlobular bile-ducts, filled with a blue mass between the lobules ; and 

 from these fine branches can be seen to pass into the lobules, within which they form a 

 polygonal meshwork over and between the hepatic cells. {Indicate the bile-ducts in PI. XVI., 

 Fig. 3-) 



Stain a section hardened in Muller's fluid with picrocannine, and mount it in Farrant's 

 solution. 



EXAMINATION (L). Note the same arrangement as above, only the hepatic cells are 

 better preserved, and their nuclei stained. 



(H). Select a large interlobular bile-duct and observe its lining of low columnar epithelium, 

 and, it may be, sections of a mucous gland in its walls. The fusiform nuclei of the non-striped 

 muscle in the wall of the bile-duct are stained red. Trace now the intra-lobular bile-capillaries 

 or channels, and observe their polygonal shape, i.e., exactly the shape of the liver-cells, the 

 plexus they form over and between the hepatic cells, whose nuclei are stained red. The bile- 

 capillaries are much smaller than the uninjected spaces of the blood-capillaries. 



In section the blue point indicating a section of a bile-capillary is found in the angle 

 where three or more cells meet. They are never found between the liver-cells and blood- 

 capillaries, and are always separated from the capillary blood-stream by a part of one or 

 more liver-cells. 



Isolated Liver-cells. Scrape the surface of a section of a liver, and diffuse the scraping in 

 salt solution on a slide. Compare p. 1 3, where these cells are described. Re-examine the 

 osmic acid and picrocarmine preparations of the liver of the rabbit and newt, and in the latter 

 study the intra-cellular plexus. 



Oil-particles within Liver-cells. These are very common in stall-fed animals e.g. ox and 

 are readily recognised by their highly refractive appearance, and by the action of osmic acid, 

 which blackens them in a very short time. 



