14 
t>. E. SALMON. 
become extensively inliltrated with cells, often forming masses of 
embryonal tissue which, pushing upward from the submucosa by 
continued multiplication, furnish the old ulcer with its projecting 
button-like slough. 
We have here two diseases, therefore, clearly defined and pro¬ 
duced by entirely different organisms. But they are not always 
uncomplicated, since we occasionally find both of them in the 
same herd at the same time. The germ of swine-plague seems to 
be a widely distributed organism and nearly always has pathogenic 
properties, though its virulence is not always sufficient to enable it 
to destroy swine. That is, in all but its pathogenic qualities it is 
identical with the germ of rabbit septicaemia; ‘with that of fowl 
cholera; with that of the disease called bv the Germans wildseuche. 
We have found a variety of this same germ frequently present in 
mucus from the nostrils of healthy pigs and possessing sufficient 
virulence to kill rabbits by inoculation. 
The presumption from these facts is that this germ is widely 
distributed, that under certain conditions when the lungs are weak¬ 
ened by irritation and disease which may result from overcrowding, 
inhaling dust, or exposure to the inclemencies of the weather, 
it may invade the lung tissue, increase its pathogenic properties 
and in certain cases become a virulent communicable disease. 
The hog cholera germ is so far as we know peculiar to that 
disease. It has not been described as present in the diseases of any 
other species of animals, except when these are produced by inoc - 
ulation. In its general biology it has many features in common 
with the bacillus of typhoid fever of man. 
Now what is the nature of hog cholera? Prof. Law and the 
writer have frequently referred to it as a contagious fever, but a 
recent author insists that it is not a contagious disease at all and 
that it is a strictly^ infectious disease. There is a good opportunity 
for hair splitting here, but let us not be beguiled by word-juggling 
when we have the facts before us. Hog cholera is a bacterial 
disease; it is communicable from animal to animal by inoculation; 
when a diseased animal is introduced into a herd the malady rap¬ 
idly progresses until nearly every animal in the herd becomes 
affected; the virus may be and is carried into all parts of the conn- 
f 
