84 REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 



Holt cultures from the soil after a few days showed immense num- 

 bers of .bacteria. From this soil rabbits were inoculated from time 

 to time by stirring up a little soil in some sterile beef infusion and 

 injecting the clear supernatant liquid hypodermically. The soil was 

 infected September 17, 1887. The appended table gives the inocula- 

 tions into rabbits to test the virulence of the soil. The rabbits which 

 succumbed died of hog cholera, as indicated by the lesions and the 

 bacteriological examination: 



The above table shows that infected soil kept moist and at a range 

 of temperature from 60 to 95 F. retained its virulence for rabbits 

 from two to three months. Roll cultures made at this time showed 

 that other bacteria and fungi had found their way into the pot 

 of soil, but no hog cholera bacteria could be detected. This and 

 other reasons drawn from observations of this germ lead to the conclu- 

 sion that the life becomes extinguished with its pathogenic effect on 

 rabbits. This phase of the question is not to be overlooked, for even 

 if a germ should not longer prove pathogenic, it may regain its orig- 

 inal virulence under certain unknown circumstances. The infec- 

 tious quality of this soil when a month old was demonstrated on pigs 

 by feeding two directly with a tablespoonful each. One showed no 

 disease; the other, unable to rise on the eighteenth day, was killed. 

 The mucosa of the lower ileum and of the entire large intestine was 

 completely necrosed. The intestinal walls were so thick that they 

 failed to collapse when slit open, and were very brittle. Bacterio- 

 logical examination and rabbit inoculation confirmed the diagnosis of 

 hog cholera. 



A pot of sterilized soil which had been saturated throughout with 

 hog cholera germs was placed, December 16, 1887, in the grounds of 

 the Department of Agriculture to test its vitality when exposed to 

 natural conditions. January 5 a rabbit was inoculated from the soil 

 on the surface of the pot. It died January 16 of hog cholera. Dur- 

 ing the period from December 16 to January 5 the germs had been 

 subjected to alternate freezing and thawing several times without 

 being destroyed. On February 1, one and a half months after in- 

 fection, the virulence of the same soil was tested on a second rabbit. 

 A severe cold had prevailed since the first inoculation and a thaw 

 was now upon us. The rabbit died of hog cholera on the eighteenth 

 day, indicating that the number of bacteria inoculated must have 

 been very small, and that most of them had already perished: On 

 February 23 another rabbit was inoculated from the surface soil of 

 the same pot. This also died of hog cholera on the eleventh day. 

 Subsequent inoculations remained without effect. Both experiments 

 show that the bacteria perished between the second and third month. 

 These and additional experiments now in progress will be reported 

 more in detail hereafter. 



