264 Hog Cholera. 
stock dealers, castrators and wandering gypsies (the latter by 
taking with them the hog carcasses and throwing the viscera 
about in different pastures) contribute materially to the spread 
of the contagion. 
In herds of hogs which have been healthy the disease is in 
most cases introduced by sick animals, and not alone by those 
in which acute symptoms may be detected, but also through the 
so-called runts in whose bodies the filterable virus may also be 
concealed. Infection may also occur during the pasturing of 
the animals, in the piggeries, during driving on highways or 
transportation in railroad cars, which have been contaminated 
by the excrements of affected animals days or weeks previously. 
The contagion may be spread from one locality to the other 
by flowing water, into which carcasses of hogs have been thrown, 
and carcasses which have been left in pastures or which have 
not been buried satisfactorily may also occasionally be the cause 
of an outbreak of the disease. 
Although hogs of all breeds and of any age may become 
affected with hog cholera, the higher bred stock and young hogs 
are much more susceptible to the disease. Sucking pigs become 
affected only very exceptionally, and as a rule the influence of 
age is especially marked in localities in which the disease has 
existed for a long time. Thus during the first years of the 
existence of the disease in Hungary the older hogs became 
affected quite frequently, while since that time the disease is 
confined more and more to younger animals. The greater 
resistance of the older animals in infected localities is in all 
probability due to the fact that they passed through a mild form 
of the disease while young. 
Pathogenesis. According to the most recent experimental 
investigations the disease is without a doubt caused by a fil- 
terable hog cholera virus, which enters the body fluids and multi- 
plies there. It causes directly a febrile condition, with acute 
catarrh of the mucous membrane, and in case of a severe infec- 
tion death results with manifestations of hemorrhagic septi- 
cemia. In the great majority of cases however secondary inflam- 
matory changes of different organs may become associated with 
the general blood infection. Such secondary changes occur espe- 
cially in the pharynx, stomach and intestines, in the correspond- 
ing lymph glands and in the lungs, being caused without a doubt 
by the bacillus suipestifer or the bacillus suisepticus. The 
etiological part of these organisms came into the proper light 
only after the virulence of the filtered blood of affected animals 
had been established. 
Contrary to the former conception by which the bacillus 
suipestifer was considered as the original and true cause of the 
disease, there now exists hardly any doubt that it participates 
only in a secondary manner, yet though it is only granted an 
inferior part in the transmission of the disease it is very active, 
