BLACK LEG 243 
and demonstrated that the disease could be produced by inoculating 
susceptible animals with it. Since that time both the organism and 
the disease have been studied by many investigators. The most 
extended investigations in this country have been made by the Bureau 
of Animal Industry. 
Geographical distribution. Black quarter exists to some extent 
in nearly every country in the world. It is reported as occurring in 
the most northern latitudes in which cattle are kept, as well as in the 
temperate and tropical zones. 
"In Europe, it occurs on the pastures on the Alps, where for five 
months in the year the ground is covered with snow and ice and in 
America it is quite common in certain northern districts. It has been 
reported from Asia and from Northern and Southern Africa. 
In the United States, it prevails to a greater extent than is generally 
supposed. The states and territories which, according to the reports 
of the Bureau of Animal Industry, suffer most from it are Texas, 
Oklahoma, Kansas, Nebraska, Colorado, North and South Dakota 
and New Mexico; but a number of the other Western States are 
badly infected. Many of the states east of the Mississippi river have 
infected localities, but in a few of the Eastern and Southern states it 
seems not to exist. During the last few years infected localities have 
been found in New York where there has been an annual loss from 
this disease, but where, prior to recent investigations, the cause of 
death has been attributed to poisoning. 
Etiology. Black leg is caused by Bacillus Chauvaei. This organism 
varies from 3 to 6 in length and from 0.5 to 1.4 in width. The ends 
are rounded and it produces spores. It stains readily with ordinary 
aniline dyes and also after the gram method. In cultures long involu- 
tion forms are often observed. It is anaérobic. In suitable culture 
media under anaérobic conditions or in animal tissues (other than 
blood) it multiplies rapidly with the evolution of gas. The presence 
of spores renders it very resistant to natural destructive agents and to 
common disinfectants. The bacillus of black leg or its spores are 
supposed to gain entrance to the tissues of animals through abrasions 
of the skin or, possibly, the mucous membranes of the mouth or 
intestine. 
The period of incubation is not positively known in cattle but it is 
very short (three to five days). Guinea pigs inoculated with a culture 
of the organism die in from one to three days. 
