WITH THE MICROSCOPE. 139 



tigation of the structure of the liver is somewhat difficult, owing to 

 the numerous distinct tissues- which compose the organ and their 

 intimate connection with each other. 



Lobules of the Liver, The arrangement of the lobules in most 

 livers is very different to that of the pig. In the latter there are 

 distinct lobules, each being inclosed in a capsule of fibrous tissue. 

 In that of most animals, however, although there is a mapping out 

 of the entire organ into small elementary organs, or lobules, these 

 are not separated from each other as in the pig, but the capillaries of 

 one lobule communicate at various points with those of adjacent 

 lobules. They are not separated by fibrous or other tissue, and no 

 structure answering to the description given of Glisson's capsule, can 

 be demonstrated in this situation. Great confusion with regard to 

 the nature of the " lobule," has arisen from observers considering 

 the pig's liver as the type to which others should be referred, whereas 

 its arrangement is exceptional and totally different from the human 

 and most mammalian livers. 



Separate pieces of liver the size of half an orange may be 

 injected without difficulty. In one the portal vein may be filled ; 

 in another the hepatic vein ; in a third the artery, and in a fourth 

 the duct, or two or more of these tubes may be injected in the same 

 specimen. The portal vein, the artery, and the duct run together, 

 while the branches of the hepatic vein run by themselves, so that in 

 sections where the vessels are large, the student will soon have to 

 distinguish the different tubes. 



Portal Vein. The general arrangement of the portal vein may 

 be easily demonstrated by injecting one of the large trunks of this 

 vessel. Any of the ordinary injecting materials may be used, but I 

 prefer the Prussian blue injection to which sufficient gelatine has 

 been added to cause it to set firmly. It is desirable not to attempt 

 to make a very complete injection, but to leave the capillaries, in the 

 centre of the lobules, in an uninjected state. 



Hepatic Vein. The injecting pipe may be placed in one of the 

 branches exposed on the cut surface of the liver. The injection 

 runs~ very readily, and upon examination it will be found that the 

 capillaries in the centre of the lobules only are filled. The 

 portal vein may be injected in one part of a liver, and the hepatic 

 vein in another part. Sections of the lobules in which the latter has 

 been inj.ected, of course form the exact complement of those of the 

 former. In the one, the central portion of the lobule has- been 

 injected, while in the other, the injection is confined to the vessels 

 and capillaries at the circumference of the lobule. By injecting the 

 portal and hepatic veins in the same part with different colours, these 



