GEOGRAPHICAL DISTRIBUTION 



179 



more common in cattle, so that we must consider not only the 

 effect of the disease upon beef and milk producing animals 

 but also upon swine. Tuberculosis is more acute with hogs 

 than with cattle, and there is a much greater tendency to gen- 

 eralization, consequently the parts used for human food are 

 more likely to be affected, and if there is a possibility of com- 

 municating the virus through the meat the danger is increased 

 by this peculiarity of the disease in swine." The statistics of 

 the last few years show a rapid increase in the amount of 

 tuberculosis in swine. In 1905 64,919 carcasses of hogs and 

 142,105 parts were condemned for tuberculosis. 



§ 140. Geographical distribution. Tuberculosis is an 

 exceedingly wide spread disease. In earlier times it was quite 

 prevalent among cattle in Central Europe. It seems to have 

 existed ii^ Western Asia and Northern Africa at an early date. 

 From these centers it has spread to nearly every cattle raising 

 country of the world. Its rapid spread during the last fifty 

 years is attributed to the increase in cattle exchange resulting 

 in the introduction of tuberculous animals into healthy herds. 

 It is stated that in many countries, and in large districts with- 

 in others, tuberculosis did not exist until it was introduced 

 within recent years by the importation of diseased animals. 



In countries where there has been little or no importation 

 of cattle, and in which the native breeds still exist unchanged, 

 as in many parts of Russia, Austria and Spain, in the north- 

 ern part of Sweden and Norway, and in parts of Africa, tuber- 

 culosis is practically unknown. This is true of the cattle on 

 the island of Jersey, where for more than a hundred years for- 

 eign cattle have not been introduced. 



In the United States, the disease is very widely distrib- 

 uted. It is found to a considerable extent in certain localities 

 where the climatic conditions seem to be beneficial for tubercu- 

 lous people. The explanation for this seems to be that tuber- 

 culous animals have been introduced into certain herds in these 

 districts. There are, however, large areas in which it is prac- 

 tically unknown. The Western steers that are killed in the 



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