126 KEPOKT OF THE BUEEAU OF ANIMAL INDUSTRY. 



break of swine plague which occurred in the beginning of 1887, and 

 which is reported in the preceding pages. In that outbreak the ear- 

 lier cases examined revealed only swine plague bacteria. Later on 

 both hog cholera and swine plague germs were encountered in the 

 same animal in a certain number of cases. Finally the swine plague 

 died out towards spring and only the hog cholera remained, causing 

 even at that time some very acute cases. The swine plague was the 

 original disease, the hog cholera being grafted upon it when the swine 

 plague pigs from a neighboring farm were placed in pens infected 

 with hog cholera at the station. Even as early as September, 1886, 

 some investigations in Illinois brought out the then remarkable and 

 puzzling fact of two disease germs found in the same animal at the 

 same time. 



Before describing the outbreak caused by the pig brought from 

 Baltimore to the Experiment Station, it will be necessary to briefly 

 indicate the condition of things at the latter in order to explain some 

 of the occurrences which followed. 



In the beginning of the present year a series of experiments were 

 planned to vaccinate pigs with sterilized cultures of hog cholera 

 bacilli. Experiments of this character are reported as having been 

 begun in the Annual Report of the Bureau of Animal Industry for 

 the year 1886, p. 50. These were not successful on pigs at that time, 

 and it was thought best to inject the sterilized culture liquid in large 

 quantities directly into the peritoneal cavity. Without going into 

 detail, suffice it to say that about twelve pigs were vaccinated in this 

 way, three receiving 800 cubic centimeters in doses of 100 cubic cen- 

 timeters at intervals of about one week, three 600 cubic centimeters, 

 three 400 cubic centimeters, and three 200 cubic centimeters. 



The experiment, including all inoculations, lasted from February 

 15 to the beginning of April. Owing to some accident or error in 

 the sterilization of the culture liquid this sterilization was not com- 

 pleted in some of the liquid used, although a number of precautions 

 had been taken to insure absolute sterility, which need!^ not be re- 

 counted here. One of the animals died of acute hog cholera on the 

 day following one of the inoculations. Its mate died within fourteen 

 days after the same inoculation of hog cholera. Another died within 

 twenty-four hours after one of the injections because of some injury 

 to 'the intestines during the injection. As these pigs were distributed 

 in groups of three in different pens, it was thought that the accident 

 of using incompletely sterilized cultures was limited to one pen, but 

 subsequent events showed this supposition to be untrue. 



The remaining pigs, ten in number, were carefully watched for 

 nearly two months (until May 25), and then brought together into 

 one pen to await a favorable opportunity for exposure to hog cholera. 

 There were in this lot Nos. 482, 483, 484, 490, 491, 493, and Nos. 8, 9, 

 11, and 12. There were also added Nos. 5, 6, 13, and 15, as control 

 animals. Of these animals, No. 482 died June 13, very much ema- 

 ciated and with extensive ulceration in the large intestine. No. 493 

 died July 5, of peritonitis, indirectly due to extensive ulceration of 

 the large intestine. The animal had shown previous to its death no 

 indications of illness. No. 484 died July 15, also of hog cholera. 

 The lesions of this case will serve as an illustration of the others. 



Spleen not enlarged. Considerable recent adhesions among coils of large intestine. 

 The mucosa of large intestine contains ulcers as large as silver dollars, with a black- 

 ish, irregularly gnawed floor. They only involve the mucosa. About the middle 

 of colon a tumor is. situated in the muscular coat of the intestinal wall as large as a 



