SWINE FEVER 191 



lesions have been observed in genuine cases of swine fever: Slight 

 effusion into the thorax ; attachments or adhesions of the pleurae may 

 be present or absent. Small ecchymosed spots are sometimes found on 

 the pleura costalis pulmonalis, and also on the pericardium. 



The pericardial sac may be distended with an enormous quantity 

 of bright yellow fluid, and the visceral folds studded with numerous 

 bright red ecchymosed spots. 



The Bronchial Lymph Glands are usually swollen, juicy, and similar to 

 those of the mesenteric region. 



The Lungs are sometimes marked by numerous red or reddish blue- 

 black spots of various sizes, some of which extend beyond the surface 

 of the lung, and often correspond to a single lobulus ; large centres of 

 hepatization are also often present (see Photo., Fig. 72). On section 

 some of the lungs reveal a stage of broncho-pneumonia lobularis, the 

 bronchial mucosa being swollen ; and a yellowish-red exudate is present 

 in the bronchi. 



Immunity. Billings obtained protection against the disease by 

 inoculating swine with cultures derived from mild cases of the natural 

 disease, but a certain proportion of the animals died from the effects 

 of the inoculation. Smith claims to have obtained better results by 

 injecting small doses of the virus intravenously. Schweinitz succeeded 

 in vaccinating the guinea-pig by means of soluble substances, which 

 he obtained from cultures. The same authority has recently pro- 

 duced immunity by means of an antitoxic serum obtained from the 

 blood of immune animals. A number of guinea-pigs were inoculated 

 with serum from a pig rendered immune to hog cholera, the doses 

 varying from 0'5 to 4*5 c.c. Five of the inoculated guinea-pigs died 

 of blood-poisoning; three withstood the injection, and fifteen days 

 later also resisted the otherwise deadly injection of 1-10 c.c. of a one 

 day old hog cholera culture. In another experiment, three guinea- 

 pigs eight months after being immunized still remained capable of 

 resisting the above-mentioned virulent dose. The immunity did not 

 continue for a longer period, because the serum experimented with 

 was obtained from a pig immunized a long time before. It therefore 

 appears that the antitoxic substance is only present free in the blood, 

 and capable of conferring immunity on other animals, immediately 

 after the animal is immunized ; but when already immunized animals 

 receive further inoculations of virus, a new formation of antitoxic 

 substance results. Schweinitz also produced immunity against 

 Schweine-seuche with an antitoxic serum, but it was not possible 

 with the Schweine-seuche serum to produce immunity against hog 

 cholera, or vice versa. 



