THE LIVER. 529 



stellate, reddish or brown spots are enclosed within a more yellowish-red 

 substance medullary and cortical substance (Ferrein). This variega- 

 tion proceeds from the usually unequal distribution of the blood in the 

 smallest trunks and in the capillaries, and in healthy persons it is re- 

 placed by a uniform reddish-brown color. The mottling of the surface 

 of the liver is frequently so regular as to have given rise to the suppo- 

 sition that it consists of lobes, especially as in an animal which is a fre- 

 quent subject of investigation, the Pig, they are very obvious ; but, 

 as E. H. Weber was the first to demonstrate, in 1842, in the human 

 liver nothing of the kind exists ; here, in fact, not only the secreting 

 elements, but the most important parts of the vascular system, i. e. the 

 capillary network between the portal and hepatic veins are intimately 

 connected together throughout the whole organ. Nevertheless, it would 

 be very erroneous to suppose that the secreting parenchyma of the 

 liver is everywhere homogeneous. Ultimate segments may be observed 

 in it, which have a certain independence, although they are in nowise 

 isolated. These hepatic lobules, as they may be called, if the term be 

 used in its most general signification, or hepatic islets, are thus pro- 

 duced : 1. The smallest branches of the afferent and efferent blood- 

 vessels, the vence inter- and intra-lobulares (Kiernan) are distributed at 

 pretty equal intervals through the whole liver, so that a portion of he- 

 patic substance of J-J-1 line in diameter, is always found to give origin 

 in its interior, to a small twig of the hepatic vein receiving externally a 

 certain number of the minutest branches of the portal vein and of the 

 hepatic artery ; and, 2, The hepatic ducts do not commence irregularly 

 in the parenchyma, but are so disposed that they invariably arise at a 

 distance of i-J a line from the origins of the hepatic veins and take 

 the same course as the finest ramifications of the portal vein. In this 

 manner little masses, containing only secreting parenchyma, capillaries 

 and the origins of hepatic veins, are marked out in the liver ; whilst in 

 their interspaces, together with parenchyma and capillaries, lie the ulti- 

 mate branches of the portal vein and hepatic artery and the origins of 

 the hepatic ducts, which, as they do not approach the masses from one, 

 but always from many sides, and are also supported and partially united 

 by connective tissue, form, if not complete, at all events partial zones 

 around them. 



The livers of those animals which present lobes (Polar Bear, J. Mutter, 

 Pig), are of the greatest value in comprehending the structure of the 

 organ, arid I therefore here subjoin an account of the structure of the 

 Pig's liver. If we examine this organ in sections or otherwise, it is al- 

 ways seen to be divided into numerous small, rounded, polygonal, not 

 very regular arece of tolerably uniform size (J 1 J lines), which consist of 

 the proper parenchyma of the liver and are bordered by whitish parti- 



34 



