DR. LEGEAR'S STOCK BOOK. 309 



Northern cattle taken into the infected district contract this 

 disease usually the first summer, and if milk cows or fat cattle, 

 nearly all die. Calves are much more likely to recover than 

 adult cattle. Calves which survive are not again attacked, as a 

 rule, even after they become adult. Experience shows that the 

 disease is not communicated by animals coming near or in con- 

 tact with each other. Cattle from the infected district first in- 

 fect the pastures, roads, cars, etc., by the mature cattle-tick 

 dropping from their bodies; and susceptible cattle obtain the 

 virus (poison) from the young ticks which hatch out from eggs 

 deposited on the ground, and which crawl upon them. But if 

 sufficient freezing takes place during the winter season, these 

 infected pastures, etc., will be free from any attack next season, 

 as all the ticks have been killed. 



The investigations made by the Bureau of Animal Industry 

 prove that ticks which adhere to cattle from the infected dis- 

 trict are the chief means of conveying the infection to non-in- 

 fected cattle; that the disease is never transmitted by the saliva 

 (spittle), the urine, or the manure through eating of foods con- 

 taminated by these excretions. The feet of cattle are not capa- 

 ble of carrying the germs. Grasses and pond water of the 

 infected districts of the Southern States do not cause the disease 

 when given to cattle. In studying the causation and prevention 

 of this disease, the tick theory has attracted the most attention, 

 and it stands to reason that if cattle could be freed from this 

 parasite when leaving the infected district, they would not be able 

 to eause the malady. That this is true has been conclusively 

 proven by recent experiments in connection with the Texas Ex- 

 periment Station near Bryan in co-operation -with the Missouri 

 Experiment Station at Columbia. Ten Texas cows covered with 

 ticks were forced to swim through a large dipping vat made for 

 such purposes, and afterwards sent by car to Columbia, Missouri. 

 Missouri cattle were put in the pasture with the Texan cattle, 

 and remained there for a period of 79 days, but failed to contract 



