INFECTIOUS DISEASES 205 



the hemorrhagic septicemia group. The Bacillus suisep- 

 ticus is a short, bipolar-staining, polymorphic, nonmotile 

 organism, and does not form spores. TJie organism 

 grows readily on practically all culture media, aerobically 

 or anaerobically. It does not liquefy gelatine or coagulate 

 milk, and is not stained by Gram's method. 



Its vitality is prolonged for from five to fifteen days 

 in soil, feces, and water when not exposed to sunlight, but 

 is destroyed in two or three days by desiccation, and is 

 easily destroyed by weak antiseptics. The organism is 

 killed in twenty minutes by a temperature of fifty-eight 

 degrees Centigrade. 



Fowls, rabbits, and guinea pigs are susceptible to the 

 pathogenic action of these organisms. The virulence of 

 the Bacillus suisepticus is quite variable and is likely to 

 vary with suddenness. Intrapulmonary injections into 

 swine usually produce multiple catarrhal pneumonia 

 succeeded by necrotic pneumonia. 



Source of infection. The Bacillus suisepticus, like 

 the other representatives of this group, are widespread. 

 They are frequently found in the respiratory passages of 

 normal swine. Their virulence is variable, and it seems 

 plausible that some predisposing condition must exist in 

 the swine that become affected, or the organism suddenly, 

 for some reason unexplained, becomes sufficiently virulent 

 to produce the disease. In the most severe outbreaks it 

 appears that the virulent organisms are transmitted from 

 the diseased to the susceptible swine, or at least the dis- 

 ease becomes enzootic in a very short time. 



Channel of entrance. The usual channel of en- 

 trance is by way of the respiratory organs, although it is 

 possible that the organism may be successfully introduced 

 through the digestive tract or skin. 



Lesions. The very acute disease is septicemic in 

 form and is characterized by petechial hemorrhages in the 

 skin and in the serous and mucous membranes. There 

 may also be some enlargement of the lymph nodes and of 

 the spleen. The usual form of the disease is characterized 

 by catarrhal pneumonia, different areas of the lung show- 



