ETIOLOGY 73 



been noted that the bacteria of rabbit septicemia, fowl cholera 

 and Wildseuche are closely related to it. 



Becker has described a pleuro-pneumonia in lambs and 

 Evans has recently observed a septicemia hemorrhagica in 

 elephants caused by this species of bacteria. The infection 

 took place through wounds. 



The pathogenic organism associated with the lesions in 

 certain forms of broncho-pneumonia in cattle differs very 

 slightly from this. In human pathology, we find a striking 

 resemblance in Micrococcus layiceolatus to the swine-plague bac- 

 terium, especially in its manifold and varied pathogenic possi- 

 bilities and its frequent presence in normal saliva. 



The fact should be recognized that experimentally the 

 different varities or forms of this group {Bacterium septi- 

 ccmiae /icmorrao-icac Hueppe, Pasteurella Trev.)arenot inter- 

 changeable in their pathogenesis except for the rabbit. Thus 

 an epizootic form of fowl cholera has not been produced with 

 the swine plague or rabbit septicemia organism. Further, it 

 has been shown that in the upper air passages of healthy 

 swine, cattle, horses, cats and dogs'^ there are bacteria not 

 distinguishable in their cultural characters and their eflfect 

 upon rabbits from the swine plague bacterium. The presence 

 of this organism in the trachea of healthy pigs has been sug- 

 gested as the source of the cause of sporadic cases of swine- 

 plague. It explains the frequent association of this bacterium 

 with hog cholera and other maladies. What the conditions 

 are by which this organism is enabled to produce disease in its 

 host have not been clearly pointed out. 



If the rabbit is taken as the animal on which to test the 

 pathogenesis of the bacteria belonging to the swine plague 

 group, we find that those from different sources are very simi- 

 lar. In nature, the bacteria of swine plague, rabbit septi- 

 cemia, fowl cholera, and those located in the normal upper air 

 passages of the various species of animals mentioned exist, 



*The investigations thus far made show these bacteria to be present 

 in 4S per cent of health}' swine, 80 per cent of cattle, 50 per cent of 

 sheep, 16 per cent of horses, 90 per cent of cats, and 30 per cent of dogs. 



