THE CONQUEST OF DISEASE 



90 per cent, of cases. Sometimes 150 cows 

 would die on a ship from this disease. Not 

 only was the loss of cattle heavy but the repu- 

 tation of American cattle in foreign markets 

 was damaged. The disease was unmanageable 

 because its nature was not understood. The 

 way the investigators went after this plague, 

 and the problems which they solved reflects 

 much glory upon the scientific spirit of this 

 country. Briefly, they pursued the methods of 

 Pasteur in his researches in diseases of animals. 

 They identified the cause of the disease as a 

 microscopic parasite in a certain cattle tick. 

 They experimented with these ticks upon 

 healthy animals. They hatched the ticks in the 

 laboratory and placed them upon northern 

 cattle and produced the disease. Then meth- 

 ods for identifying and destroying the danger- 

 ous ticks were perfected. Finally northern 

 cattle, to be taken south for breeding purposes, 

 are inoculated with the blood of southern cattle 

 and given a mild attack of the disease which 

 renders them immune for the rest of their lives. 

 These experiments have reduced the loss from 

 Texas fever among such animals from 90 per 

 cent, to 10 per cent. Researches are now under 

 way with the aim of finding a means of destroy- 



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