Pathogenicity. 261 



or recover completely. Sueli recovered animals are subsequently 

 immune against artificial, as well as against natural infection. 



Animals artificially infected in the above manner may 

 readily transmit the disease to healthy hogs by cohabitation, 

 and their blood even in a filtered condition, and in small quan- 

 tities, is also infectious. By serial re-inoculations the virus may 

 be propagated from generation to generation. 



'The artificial affection is, although with less certainty, also 

 successful, by the administration of blood and blood serum in 

 gelatine capsules per os, or by feeding the same with food, when 

 unfiltered material acts more strongly than filtered. The virus 

 is as a rule also present in the bile and the urine, while the intes- 

 tinal contents frequently prove noninfectious (IJhlenhuth). By 

 feeding internal organs of diseased hogs the disease may readily 

 be produced artificially. Other species of animals aside from 

 the hog are not susceptible to the virus. 



Tenacity. Fluid material containing the virus retains its virulence at room 

 temperature for 10 to 14 weeks. Heating for one hour at 60 to 70 "C destroys 

 the virus, while in the dried condition subjected to 72 to 76° it requires an hour 

 to destroy its virulence. Blood frozen below ■ — 18° and thawed out after 24 

 hours, proved fully virulent, likewise blood which had been dried for three days. 

 The addition of a 1:1000 corrosive sublimate solution in the proportion of 1 to 

 2, or of a 5% glycerine-carbolic acid solution in the proportion of 2:5 does not 

 destroy the virus inside of 8 days; on the other hand the virus in serum is rendered 

 ineffective by the addition of 2% formalin in 15 days, by 2.5% antiformin in 

 2 hours. The virus in old putrefied organs loses its virulence in eight days 

 (Uhlenhuth). 



Besides the filtrable virus, two species of bacteria, the 

 bacillus suipestifer and the bacillus suisepticus, play an impor- 

 tant part in the etiology of hog cholera. The secondary affec- 



Fig. 46. Bacillus suipestifer. Agar cul- Fig. 47. Bacillus suipestifer, with fla- 

 ture, fuchsin staining. gella. Agar culture. 



tions of the intestines and of the lymph glands or of the lungs 

 are usually produced by the pathogenic action of these bacteria. 



1. The bacillus suipestifer (Bac. cholerae suis) resembles 

 the colon bacillus and belongs to the paratyphus B-group. It 

 is motile, possessing peritrically arranged (3-9) flagellae, and 

 multiplies exclusively by fission (Fig. 46 and 47). In tissues 



