Pathogenesis. Anatomical Changes. Sj'uiptonis. 529 



Eisenmann found necrotic foci in tlie liver associated with chronic inflam- 

 mation in some eases of swine erysipelas. Caseous foci are sometimes found in 

 the liver of sheep and calves due to pseudo-tubercle bacilli. These foci bear consider- 

 able resemblance to necrotic lesions in the process of softening. 



Pathogenesis. The necrosis bacillus is generally arrested 

 in the smallest branches of the portal vein, or occasionally in 

 the hepatic artery. Multiplication takes place there and the 

 bacilli pass through the vessel wall and penetrate into the sur- 

 rounding liver tissue. The center of the lesion gradually be- 

 comes necrotic and the bacilli are to be found in the peripheral 

 parts arranged in radiating bundles of filaments. An inflamma- 

 tory reaction sets in around the necrotic area, produced in part 

 by the products of tissue destruction and bacterial toxin and in 

 part by the necrotic tissue acting as a foreign l)ody (Mc- 

 Fadyean). 



Anatomical Changes. The liver, which may be more or less 

 enlarged, is either normal or slightly yellowish in color. The sur- 

 face of the organ shows sharply defined rounded protuberances 

 of a light brown or yellow color. These are of a firmer con- 

 sistency than the surrounding tissue. The capsule of the liver 

 covering the superficially placed nodules is thickened and cov- 

 ered with a thick layer of fibrin. Some of the superficial nodules 

 may be eroded and covered with a purulent liquid. There is 

 often secondary sero-fibrinous peritonitis, which is most marked 

 in the neighborhood of the liver. 



When the disease has been in existence for a long period 

 the nodules comprise a dry necrotic center, a zone in which the 

 inflammatory reaction has produced softening and an external 

 capsule of fibrous tissue. Finally the central part becomes con- 

 verted into a viscous yellow material resembling pus, and is 

 surrounded by a fibrous capsule which may measure 3 mm. in 

 thickness. 



In cases of chronic swine erysipelas Eisenmann found the liver reduced in 

 size and beset with white or yellowish centers. 



Symptoms. According to Berndt the symptoms are inap- 

 petence, high fever, weakness and painfulness of the liver. The 

 animals move with difficulty, respiration is accelerated and 

 shallow, pressure over the liver causes pain. After three days 

 the animals become very weak and lie down continuously. Res- 

 piration is very rapid and difficult, tliere is constipation fol- 

 lowed by diarrhea, the ,al)domen is joainful, the temperature 

 falls, jaundice sets in and the animals soon die. Otto saw two 

 cases in which there were s^anptoms resembling those- of par- 

 turient paralysis after the disease had been in existence for 1 

 to 11/^ weeks. 



In cases where the number of lesions is small, or where sub- 

 sequent processes are less rapid, the symptoms are not severe or 

 there may be no evidence of any disturbance of health. 



