METHODS OF DISTRIBUTION 289 
found in countries where cattle are kept. It is said not to occur 
in Africa, and until recently it has been absent from China and 
Japan, having lately been introduced with imported cattle. In 
the western part of the United States, among the cattle living out 
of doors most of the time, it is rare or absent. In general it is 
most abundant in localities where the cattle are housed for a con- 
siderable part of the year. It is consequently most abundant in 
northern countries, and appears to be most widely distributed in 
northern Europe. 
It is practically impossible to state the percentage of cattle 
suffering from tuberculosis. Among the animals examined in the 
slaughter houses of Denmark it has sometimes appeared that more 
than half of the cows are tuberculous. From these high figures 
the percentage has ranged down to ro per cent. or even lower in 
some places, and, in fact, is so variable that no general averages 
are of any significance. In the United States the results differ 
so widely that figures have, as yet, little value. Sometimes every 
animal in a herd is found to be tuberculous, while other whole 
herds are entirely exempt. In the eastern States the percent- 
age is large, and in some localities it appears to approach the 
figures given for Denmark. When the numbers of infected animals 
in a herd range from o to 100 per cent. it is evident that no result- 
ing average would be of any significance. 
Increase of the Disease——lIs bovine tuberculosis on the 
increase? Statistics are so uncertain as to make any conclusion 
difficult. Certainly we hear much more of the disease than we 
did a few years ago, and the percentages reported to-day are much 
higher. The knowledge of the disease is, however, of very recent 
date, and the increasing interest in the subject has caused a more 
and more careful inspection of slaughtered animals, which has 
resulted in a constant increase in the number of reported cases. 
Even in the same slaughter houses and under the same manage- 
ment, the percentage of tuberculous animals reported has been 
increasing year by year in such a way as to seem to indicate an 
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