50 SWINE PLAGUE 
It has already been noted that the bacteria of rabbit septicemia, fowl 
cholera, Wildseuche and septicemia hemorrhagica of cattle are closely 
related to it. In human pathology, there is a striking resemblance 
between M. lanceolatus and Bact. suisepticum, especially in its varied 
pathogenic possibilities in rabbits and their frequent presence in 
normal saliva. 
It should be recognized that experimentally ‘the different varieties 
or forms of this group (Bactertum septicemiae hemorragicae Hueppe, 
Pasteurella Trev.) are not interchangeable in their pathogenesis 
except for the rabbit. Thus an epizodtic form of fowl cholera has 
not been produced with the bacterium of swine plague or of rabbit 
septicemia. Further, it has been shown that in the upper air passages 
of healthy swine, cattle, horses, cats and dogs* there are bacteria not 
distinguishable by the usual methods in their cultural characters and 
in their effect upon rabbits from the swine plague bacterium. The 
presence of this organism in the trachea of healthy pigs explains the 
frequent association of this bacterium with hog cholera and other 
maladies. The conditions necessary for this organism to produce 
disease in its host have not been explained. 
If the rabbit is taken as the animal on which to test the patho- 
genesis of the bacteria belonging to the swine plague group, we find 
that those from different sources are very similar. In nature, the 
bacteria of swine plague, rabbit septicemia, fowl cholera, and those 
located in the normal upper air passages of the various species of 
animals mentioned exist, possessed of marked variation in virulence, 
that is, there are those that will kill a rabbit in from 16 to 24 hours 
when inoculated subcutaneously with a pure culture and those that 
require from 3 to 10 days, or even weeks, to destroy life. With the 
variations in the time period, we have corresponding differences in 
les'‘ons. The virulent forms produce bacteriemia while the attenuated 
varieties excite a severe purulent infiltration about the place of 
inoculation and exudates on one or more of the serous membranes. 
Conversely, it has been shown that rabbits possessed of a certain 
amount of natural or artificially produced resistance will, when 
inoculated with a virulent culture, die after the same period of time 
and with lesions similar to those produced by the attenuated virus 
in the susceptible rabbit. 
*The investigations thus far made show these bacteria to be present in 48 per cent. 
of healthy 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. 
