88 DISEASES OF SWINE 



cause it has been found that hogs do not always develop this dis- 

 ease when exposed to or fed with this organism, and it is found that 

 the disease often produced by these germs is not catching to other 

 animals as is the genuine cholera. So that at this time it can be 

 positively stated that the hog-cholera bacillus is not the direct 

 cause of hog-cholera, but is a germ which makes its appearance after 

 the disease is established. 



Ultramicroscopic Virus is True Cause of Cholera. — Repeated 

 experiments with the blood of animals sick with cholera have 

 proved that there is some poison or virus in the blood of the cholera 

 hog which is so small that it even cannot be seen with the highest 

 power of the best microscopes, and this virus is also so fine in 

 character that it will pass through the finest porcelain filters. This 

 is what is called an ultramicroscopic virus, and it is this ultramicro- 

 scopic virus which is now generally agreed to be the cause of hog- 

 cholera. 



So that we are now forced to say that the direct cause of the 

 disease (hog-cholera) is some invisible virus, which is so small that 

 we are unable to observe it even with the best of microscopes, and 

 which is capable of passing through the finest filters. Such an 

 organism is what is called ultramicroscopic. By the word "ultra- 

 microscopic" we mean something that is so small that we are unable 

 to see it with the most powerful magnifying glasses with which our 

 modern microscopes are provided. This, then, is the sort of germ 

 which produces cholera. It is so minute that we are unable to see 

 it even with the microscope, yet we are certain that it is there, be- 

 cause we can take the blood or infected discharges of the animal 

 and produce the disease in healthy animals. 



How Germ Enters Body. — The virus of cholera enters the body 

 of the healthy animal probably, in the majority of cases, through 

 the mouth, and thence through the stomach and bowels. It is ob- 

 tained most frequently by eating some diseased articles of food, 

 such as carcasses of hogs which have died of cholera or discharges 

 from sick animals. 



Spread. — There are hundreds of ways by which these disease- 

 producing discharges may be carried to the healthy hogs, as will be 

 pointed out under the head of Predisposing Causes and Preventive 

 Treatment. The most common ways are by direct contact with 



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