690 CONGESTION OF THE LIVER. 



In the first, the secretion of bile being natural, its excretion 

 or outpouring is impeded by the pressure upon the lobules 

 or bile-ducts, exerted by means of the engorged vessels. 



In the second, the increased supply of blood on to a certain 

 point provides an increased pabulum for the secreting struc- 

 tures, the product of which the bile-ducts are not at once able 

 to carry away. Very shortly, however, this congestion, if con- 

 tinued, or even if frequently repeated, will tend to a result the 

 opposite of augmentation of bile-secretion. 



Both these conditions of vascular congestion, as far as the 

 liver itself is concerned, may be regarded as passive, while, if 

 kept up for any length of time, they tend to bilious contamina- 

 tion of the blood, and, when repeated, to serious structural 

 changes of the liver, and are the chief source of abdominal 

 dropsy. Their attendance upon or preceding such changes as 

 cirrhosis may be accounted for by remembering that this con- 

 tinued and repeated constriction of the lobule-cell is Hkely 

 both to impair its nutrition and power of reproduction, as also 

 that, like other structures, when their natural functions are not 

 duly called into operation they are liable to atrophy and 

 degenerate. 



The several conditions of hypersemia and turgescence of 

 hepatic structure in the horse during life, if we were to judge 

 by clinical history alone, might seem of rather rare occurrence ; 

 but, in the light of after-death examinations, they are evi- 

 dently of frequent enough existence. 



In our post-mortem records it is not uncommon to find 

 notices of livers enlarged in every direction, with capsule 

 tightened and distended ; while section of the structure dis- 

 closes patches and streaks of dark brown, surrounded with 

 tissue of a much lighter colour. These are but modifications 

 of the so-called nutmeg liver. The dark patches are engorged 

 hepatic veins, occupying the centre of the liver lobules, the 

 lighter markings corresponding to the minute ramifications of 

 the portal veins, the pallor probably in some cases owing its 

 existence in part to minute vessels rendered empty by com- 

 pression, to fatty material in cell-structures, or to increase in 

 amount and alteration in character of the interconnective- 

 tissue. 



h. Causation. — These varied forms of hypersemia, or conges- 



