422 TEE DIGESTIVE APPAEATUS IN MAMMALIA. 



border is attached, almost in the median plane, to the posterior face of the 

 diaphraom, and even to the inferior abdominal parietes. At its free border 

 is a fibrous cord (the round ligament), formed by the obliteration of the 

 fcBtal umbilical vein. By its upper part, it penetrates a secondary notch 

 in the middle lobe, and is prolonged on the anterior face of this to the point 

 where the vena cava traverses the diaphragm. 



Stkuctubb. — As elements in its structure, the liver offers for study : 

 I, A serous membrane; 2, K fibrous capsule ; 3, The j^roper and fundamental 

 tissue of the organ. 



1. Serous Membrane. — This membrane is only an expansion of the peri- 

 toneal bands or ligaments already described, and of which the two, on 

 arriving at the organ, separate to become developed on its surfaces, and to 

 completely cover it, except in the anterior and posterior fissures. 



2. Fibrous, or Glisson's Capsule. — This, the proper envelope of the 

 liver, is formed by a very fine fibrous membrane, closely adherent to 

 the preceding layer on the one side, and to the tissue of the liver on the 

 other. It penetrates the substance of that tissue in passing around the 

 vessels lodged in the posterior fissure, and from its inner face it sends a 

 multitude of lamellar partitions, which separate the hepatic granulations, 

 and form a veritable framework in the interior of the organ. The 

 presence of this capsule has been denied, but its existence is not to be 

 doubted in all the domesticated animals ; it is particularly well developed 

 in Euminants. 



3. Proper Tissue of the Liver. — The proper substance of the liver is 

 distinguished by its bluish-brown or violet hue, the shades of which vary 

 much according to the subjects. It is heavy, compact, and so friable that it 

 is crushed by the most moderate pressure. It is composed of polyhedrie 

 granulations from l-20th to 1-lOth of an inch in diameter, which are 

 readily enough distinguished from one another through the peritoneum on 

 the surface of the organ, particularly when the septa thrown in between 

 them from Glisson's capsule are hypertrophied from some slight chronic 

 irritation. 



Sometimes the hepatic lobule is uniform in colour throughout ; often it 

 shows a red central point, with a yellow circle around it, and an interrupted 

 red ring circumscribing this again, and which communicates with a similar 

 circle belonging to the adjoining lobules, so as to compose a network at the 

 surface of the gland ; at other times the lobules are yellow at the centre and 

 red at the circumference. All these appearances, the study of which at one 

 time was considered of much importance, are uncertain, and may vary in a 

 thousand ways, in combining with one another ; so that they really demand 

 but little attention, due as they are to the greater or less degree of plenitude 

 of the difierent vessels entering the lobule. 



As the liver is composed of lobules placed beside each other, we will 

 describe one ; as when its structure is well known, we will be familiar with 

 the organisation of the entire organ. 



In a hepatic lobule we find : 1, Hepatic (or biliary) cells ; 2, Biliary canal- 

 iculi (or ducts); 8, Afferent vessels; 4, An efferent vessel; 5, Lymphatics; 

 6, Connective tissue. 



Hepatic cells. — These are polygonal or round, and much resemble 

 squamous epithelium ; their diameter varies from l-500th to l-200th of an 

 inch. They are composed of a thin enveloping membrane and yellow- 

 coloured contents. The latter comprise one or two nuclei with nucleoli, 

 coloured granules, biliary matter, a small mass of a substance which has been 



