Of veterinary medicine. 147 



work results in rupture of some of the smaller blood vessels of 

 the liver and as a consequence hemorrhage. This hemorrhage 

 is not sufficient to do any harm with a first or second attack, for 

 the ruptured vessels heal and the clot becomes absorbed, leaving 

 an anaemic patch, usually white. These patches can be seen on 

 the surface of the liver under the capsule. These may vary in 

 size from V^ inch to % inch in diameter. They are old chronic 

 infarcts. These are common in old cattle and occasionally in 

 horses. 



In a more severe case rupture of the larger blood vessels oc- 

 curs; the hemorrhage is greater, and if it is a third or subsequent 

 attack, degeneration takes place to a greater or less extent. Con- 

 sequently the infarction and hemorrhage are greater. Sometimes 

 rupture of the capsule takes place with a fatal internal hemorr- 

 hage. 



Etiology of Passive Congestion (Porta!). — This depends 

 mostly upon enervation, that is, nervous prostration of the 

 animal. This is the principal cause of portal congestion. General 

 enervation is seen in influenza, pneumonia and in other affections. 

 The liver gets torpid and does not work as actively as it should. 

 The bile is not secreted in proper quantity and biUary capillaries 

 become congested, probably as a result of defective cardiac power. 

 The congestion produces pressure upon the liver lobules, inter- 

 fering with the outward flow of the bile through the minute bile 

 ducts. 



In case of pneumonia there is a different pathogenesis. 

 There is a defective cardiac power. In all bad cases of pneumonia 

 there is more or less obstruction of the arterial circulation in the 

 lungs. This is especially so in the third stage, and the obstructed 

 circulation dams up the outlet and leads to dilatation of the right 

 ventricle, which in turn prevents the blood from leaving the liver. 

 Consequently in most cases of pneumonia on about the fourth day 

 we get considerable jaundice. 



In chronic diseases of the kidneys there is an insufficiency of 

 secreting substance, and consequently an insufficient secretion of 

 the urine. This leads to ascites. 



Biliary Congestion. — Biliary congestion occurs secondary to 

 the active or the passive. It is a direct result of pressure upon 



