HOG CHOLERA 421 
called Bacterium of swine plague. In 1865 Dr. Budd of England 
published a very exhaustive description of pig typhoid which corre- 
sponds to the lesions of hog cholera. There are references to a disease 
among swine in France in 1822 that’ appears from the description 
given to have been hog cholera. Fleming refers to an epizodty among 
swine in Jreland in 1040. There are also numerous references to 
infectious diseases among swine in Germany and other European coun- 
tries prior to 1833. The positive diagnosis of those earlier outbreaks 
is impossible but the inference is strong that hog cholera existed at that 
time. 
In 1886, Dr. Theobald Smith discovered another bacterial disease 
among swine. It was found to be similar to the German Schweine- 
seuche both in the morbid anatomy and in the morphology and proper- 
ties of its specific organism. In naming this disease the Bureau of 
Animal Industry called it, on account of its similarity to the German 
Schweineseuche, swine plague and its organism the bacillus of swine 
plague, and changed the name of the disease described in 1885 to hog 
cholera and its organism to the bacterium* of hog cholera.t 
In 1903, de Schweinitz and Dorset discovered what they called a 
disease identical with hog cholera but which they produced with 
virus that passed through the finest porcelain filters. Subsequent 
investigations by Dorset, Bolton, McBryde and Niles showed that the 
organism known as the bacillus of hog cholera was not the cause of 
that disease but when present it was a secondary invader. They 
did not, however, deny that it possessed pathogenic properties for 
swine. 
Soon after the discovery of the filterable virus, it was found that 
the serum of hogs that had recovered from cholera possessed a certain 
amount of immunizing power against the disease and that when they 
were hyperimmunized their blood serum would produce a temporary 
passive immunity against the virus in hogs injected with it. It was 
*In 1888 the genus Bacterium was changed to Bacillus and this organism is spoken 
of since that time as the hog-cholera bacillus. 
}Billings, of the Nebraska State Experiment Station, opposed this nomenclature. 
He not only refused to accept the change but continued to write about hog cholera 
under the title of swine plague. He also denied the existence of swine plague, as 
described in the reports of the Bureau of Animal Industry for 1886. The wide dis- 
semination of his publications on this subject has unquestionably been responsible for 
‘much of the haziness concerning the distinguishing features of these maladies. 
In 1893, Drs. Welch and Clements read a paper before the International Veterinary 
Congress in which they gave a very clear history of the nomenclature of these diseases 
and in which they adhered to the one of the Bureau of Animal Industry. 
