638 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



2''ests with heated virus on Pigs. 



In order to test the effect of heated cultures upon pigs the follow- 

 ing exx)erinients were made March 1: Two animals (Nos. 102 and 

 173) received hypodermically each 9'='^ of a second and third culture, 

 twelve and thirteen days old, respectively, which had been devitalized 

 by heat. March 9 a second dose of 9*=*= was given in the same way, 

 using a fifth and eighth culture eighteen and fourteen days old re- 

 spectively. These cultures were made in beef infusion containing 1 

 per cent, peptone, excepting one, which contained about 2 per cent, 

 of blood serum in place of the peptone. After the second inoculation 

 of No. 162 a swelling appeared on one side. Both were fed with vis- 

 cera infected with hog-cholera, and placed with sick and dying pigs 

 in a large infected pen. No. 162 was found dead March 29 and No. 

 173 April 5. The appended table and notes give a summary of the 

 experiment: 



No. 162. Subcutaneous fatty tissue much reddened. Mucous membrane of stomach 

 considerably ulcerated; of small intestine deeply congested. For 8 or 10 feet above 

 the ileo-csecal valve the mucous membrane of ileum is completely necrosed. Large 

 ulcers in ca3cum and upper portion of colon. 



No. 173. Subcutaneous fatty tissue shghtly reddened. Petechias under pulmonary 

 pleura. Extravasations mider sei'osa of caecum and colon. Inflammatory adhesions 

 of large intestine with walls of abdomen. A patch of extravasation beneath peri- 

 toneal layer of dorsal abdommal wall nearly 2 inches across. Spleen very much 

 enlarged and softened. The mucous membrane of large intestine and several feet 

 of ileum necrosed and breaking down. Fundus of stomach deeply congested. 



This experiment clearly showed that this method was no protec- 

 tion to the animal when the latter was infected by feeding. 



It now became necessary to determine whether this method would 

 confer immunity uj)on animals simply exposed to the disease by co- 

 habiting with diseased animals in infected pens. Observations made 

 upon other diseases by investigators, and by us upon this disease, 

 seem to lead to the inference that it frequently depends on the quan- 

 tity of virus introduced into the system whether the disease will 

 make its appearance or not. In feeding this quantity is considerable; 

 in simple exposure in infected pens to diseased pigs the amount of 

 virus taken into the body Avith the food and drink is necessarily in 

 small and repeated doses. The following experiment was therefore 

 planned: 



Four pigs (Nos. 163, 164, 177, and 196) were inoculated March 13 

 with heated virus, each receiving 4^"*^ beneath the skin of each thigh. 

 The cultures in beef infusion with 1 per cent, peptone were about fif- 

 teen days old when heated. The second inoculation was made March 

 16 from a culture in an Erlenmeyer flask about eleven days old, and 

 containing about 50'='^ of culture liquid. Each animal received 10*'*' 

 as before. 



March 31. — These animals, together with two check pigs (Nos. 195 

 and 201) were placed in a large infected pen. Within a period of 

 three weeks from this date at least fifteen pigs died of hog-cholera 



