494 Veterinary Medicine. 



tion, or for the butcher, acts in a similar manner. Dilatation of 

 the right heart, or imperfection of the tricuspid valve is a direct 

 cause of mechanical congestion and emphysema, congestion or 

 other obstruction in the lungs has a similar effect. In short the 

 absence of valves between the right heart and the hepatic veins 

 determines a passive congestion of the liver whenever there is 

 any serious hindrance to the passage of blood through the right 

 heart and lungs. The tardy circulation through the liver (5 mm. 

 per second) also predisposes to congestion. The great develop- 

 ment of the circulatory system in the liver, and its dilatability 

 predisposes it to such congestions in a pre-eminent degree. For 

 the same reason the liver suffers in the horse that is attacked with 

 pulmonary congestion, whether as the result of over- work or of 

 heat congestion. It will also suffer from compression of the 

 lungs by false membranes or hydrothorax, or obstruction, by 

 oedema, hepatization or infarction. The toxic matters produced 

 in infectious diseases, and especially those affecting the intestinal 

 canal and its connections, are arrested in the liver and contribute 

 to hyperaemia. 



CONGESTION OF THE LIVER IN THE HORSE. 



Causes. Beside the general causes above mentioned, may be 

 specially named, musty, decomposed, and irritant fodders : those 

 which like green legumes, are easily fermented ; and those which 

 contain stimulating volatile oils or carminative principles. They 

 are also especially exposed to such causes as severe and prolonged 

 work under a hot sun, the nervous atony which causes vaso-dila- 

 tation in a hot climate, and such traumatisms as come from falls, 

 kicks, goring, and blows by shafts, poles and clubs. These 

 especially induce active congestion. The passive forms come 

 mainly from obstruction in the lungs, or heart (dilatation, right 

 valvular insufficiency, pericarditis, hydropericardium, myo- 

 carditis, fatty degeneration, endocarditis), or in the posterior 

 vena cava. 



Lesions. The congested liver is enlarged and deeply colored 

 with blood. The weight of twenty to thirty pounds is often at- 



