102 REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 



The introduction of hog cholera after the appearance of swine 

 plague was most likely due to the case first reported in these pages 

 (No. 406). 



ATTEMPTS TO PRODUCE SWINE PLAGUE WITH PURE CULTURES. 



A number of experiments were made which were designed to 

 demonstrate, if possible, the. specific nature of the bacteria obtained 

 from diseased lungs. A reproduction of the disease after the intro- 

 duction of the bacteria contained in pure cultures into the lung tis- 

 sue itself must be regarded as conclusive evidence. 



The following means of infection were tried: 



(a) By exposing pigs to a spray of culture liquid. February 17 

 Nos. 398, 400 were placed in a tight box, 3 by 4 by 2 feet, with a 

 glass top. A spray was allowed to play into the box from an atom- 

 izer, the nozzle of which was introduced through a small hole in the 

 side near the top of the box. The spray thus played across the top 



'of the box, and was continued for two hours on two consecutive 

 days, 300 cubic centimeters of culture liquid being used each time. 

 The culture was an infusion of beef, in which the swine plague bac- 

 teria (from an Iowa outbreak) had multiplied at 95 F. for two days. 

 For several days after respiration was somewhat labored, and for 

 nearly a week they ate very little. Subsequently, however, they 

 fully recovered. 



Nos. 393, 394 were exposed March 3 to a spray in the manner de- 

 scribed. The culture was made in beef infusion and was one day 

 old. The swine plague bacteria were from the Washington outbreak. 

 The spraying was continued for one and one-fourth hours, several 

 hundred 'cubic centimeters (about one-half pint) being used. No 

 symptoms of lung disease followed the spraying. No. 393 was killed 

 April 28, nearly two months later, and found perfectly sound. No. 

 394 was exposed to hog cholera April 30, and died of the acute hemor- 

 rhagic form of this disease May 17. The lungs were not he^atized but 

 dotted with numerous subpleural petecchise, characteristic of acute 

 hog cholera. 



Spraying and feeding cultures both had thus far proved ineffectual 

 in reproducing any lesions in the lungs or the intestinal tracts. Other 

 modes of introducing the virus were therefore tried. 



(b) Two pigs (Nos. 383, 385), one of which had been fed with hog 

 cholera and the other with swine plague cultures December 19, 1886, ' 

 were perfectly well March 16, on which day 5 cubic centimeters of a 

 liquicf culture of swine plague bacteria was injected into the trachea 

 of each. Owing to the thick layers of fair in the neck, intratracheal 

 injection could only be practiced by cutting down to the trachea, rais- 

 ing it with the finger, and then introducing the needle of the hypo- 

 dermic syringe. After the operation the animals were dull and refused 

 feed for one or two days; after that they were fairly well. The incisions 

 meanwhile healed up. April 28, nearly one and one-half months after 

 the inoculation, No. 385 was killed. The organs were normal; no lung 

 disease manifest. No. 383 was exposed to hog cholera in an infected 

 pen April 19, more than a month after the tracheal injection. It had 

 been apparently well during this time. It died May 11 of acute 

 hemorrhagic cholera. The autopsy notes being recorded elsewhere, 

 it suffices to state, hat the lungs were covered, as is common in this 

 disease^ v with large subpleural ecchymoses. There was no hepatiza- 

 tion suggesting swine plague. On April 4 two pigs (Nos. 389, 401) re- 



