VETERINARY MEDICINE. 681 



suipestifer Avas present in the animal furnishing the virus for inoculation, this 

 organism appeared also in the inoculated animal as a mixed infection. It 

 occurred four times in animals infected by exposure only, and In all cases 

 (3) which were recorded as having received an intravenous inoculation, also 

 in five of the six hogs which died after serum-simultaneous vaccination. As 

 for the post-mortem lesions present in animals showing this mixed infection it 

 will be seen that there is no uniformity ; that is, none which occur only in 

 such cases. Two are recorded as showing only slight lesions. B. suisepticus 

 was obtained in one case in which there were no pulmonary lesions reported. 

 In the two cases in which this species was present in the original virus it was 

 not found in the inoculated animal, nor were pulmonary lesions present. 



" To obtain more direct evidence of the effect of mixed infection with B. sui- 

 pestifer and hog cholera virus (filterable virus), experiments were carried 

 through in which pigs were infected simultaneously with cholera virus (blood) 

 and with cultures of the bacilli, in comparison with others receiving the blood 

 infection alone. The virus employed was the ' Winslow virus,' which had never 

 been found to give rise to this mixed infection in previous tests. The culture 

 of B. suipestifer employed was one which had been grown in the laboratory for 

 IS months. At the time it was isolated this strain was of less than the usual 

 degree of virulence for guinea pigs. It had not previously been tested on pigs." 

 Some control animals were placed in the pens and seven days after infection 

 showed signs of sickness. In all of these cases when B. suipestifer was not fed 

 or inoculated the bacilli were not detected. 



This experiment indicated as to mixed infection, (1) a shortening of the 

 incubatory pei"iod, (2) a greater severity of the symptoms and more rapid 

 course of the disease, and (3) an absence of any essential and uniform differ- 

 ences in the patho-anatomical changes as seen on dissection. The peculiar 

 form of exudative inflammation with necrosis of the surface epithelium of the 

 large intestine, which occurred in both of the pigs in the pen infected with 

 bacilli by feeding and in one of the pigs infected by inoculation, was present 

 also in an exposure pig which survived for three weeks. " Since this condition 

 quite regularly results from successful infection experiments by ingestion of 

 cultures of B. suipestifer alone, we must look upon it as an inflammatory reac- 

 tion due to the presence of this bacillus." 



Although the controls (exi)osed animals) became sick, B. suipestifer could not 

 be detected, and this shows that B. suipestifer infection in hog cholera is prob- 

 ably not dependent to any great extent on transference from animal to animal. 

 Any positive assertion on this question, however, must be based on more exten- 

 sive tests made under varying conditions. 



When B. suipestifer is introduced artificially, by inoculation or ingestion, 

 in conjunction with the true hog cholera virus a generalized infection with the 

 bacillus usually results. " Since infection with B. suipestifer is not known to 

 occur unassociated with true hog cholera infection, except when artificially 

 induced, a complete immunity to the latter virus should indirectly afford pro- 

 tection against the bacillar invasion as well." To what extent the bacillar anti- 

 body content in serum may add to the potency of an antihog cholera serum 

 needs still to be investigated. " In the practice of * serum simultaneous vacci- 

 nation ' accidents arising from this cause are no doubt of occasional occurrence. 

 That they are not frequent may be explained by the facts: (1) That most 

 samples of antiserum contain bacterial antibodies; (2) most samples of virus 

 do not contain bacilli ; (3) inoculations of bacillar cultures subcutaneously are 

 often ineffective." 



The agglutinins in antihog cholera serum for B. suipestifer are assumed to 

 be due mainly to a reaction against the bacilli injected with the blood in hyper- 



