THE DISEASES OF CATTLE 297 



done to the satisfaction of even the Texans. For sev- 

 eral years the "bull tick" theory was the basis for 

 many a shot at investigating veterinarians. The gist of 

 the matter was that Texas cattle through long years of 

 infection had become immune to the disease, and while 

 still carrying in their blood the deadly bacilli of the 

 disease did not themselves succumb to it. 



The Federal Government in order to prevent the 

 spread of the disease has drawn a line called a quarantine 

 line which extends from the Atlantic Coast clear across 

 the South and Southwest, running as far north as the 

 northern line of Oklahoma and southwest ' across the 

 northwest portion of Texas to the Mexican line. From 

 below this line no cattle may be removed excepting for 

 immediate slaughter. At the present time the Govern- 

 ment is experimenting in the dipping of tick-infested 

 animals with excellent results. A campaign is also being 

 carried on looking to the complete eradication of ticks 

 from the lands. This process is a long one and to be 

 successful must have the hearty co-operation of inter- 

 ested parties. 



By means of changing pastures, moving the cattle 

 back and forth and keeping all stock off certain areas for 

 definite periods, the ticks may be starved out and the 

 land freed from their presence. Twenty years ago all 

 of California south of San Francisco was infested with 

 ticks and under quarantine. Today by these methods 

 the state is free from ticks. 



The life-history of the tick furnished the means of its 

 extinction. It was found that the tick lived on an ani- 

 mal for a certain time, then dropped off., laid its eggs and 

 died. The eggs so planted developed, according to the 

 weather, in the course of thirty to sixty days. The young 



