140 FARM ANIMALS 



become infected with tubercle bacilli from man and 

 man in turn with tuberculous milk or meat. The 

 disease may be detected by the use of tuberculin, 

 which is usually administered by state sanitary 

 officers. This material gives a fever reaction in 

 diseased animals and no reaction in healthy ones. 

 They may thus be divided into two lots and the 

 infection prevented from spreading to the healthy 

 animals. Recently various German, French, 

 English and American investigators have found 

 an apparently satisfactory method of vaccinating 

 cattle so as to render them immune to the disease. 

 For vaccine tubercle bacilli from man are used after 

 being reduced in virulence. A mild form of the 

 disease is thus produced from which the animals re- 

 cover and later are not subject to tuberculosis. 



Texas Fever. This is the most important cat- 

 tle disease of the southern states and has long 

 caused serious loss to the agriculture of that part 

 of the country. Texas fever is caused by a blood 

 parasite which destroys the red blood corpuscles, 

 causes a high fever, rapid emaciation and death 

 in a large percentage of cases. The blood par- 

 asite is carried from the diseased animal to healthy 

 ones by the cattle tick and without the agency of 

 this tick Texas fever cannot be distributed. It 

 is evident, therefore, that in order to control this 

 disease effectively it is desirable to attack the 

 cattle tick. On account of the difficulty of its 

 extermination, however, and the belief by a large 

 percentage of investigators that the extermination 

 of the cattle tick was impossible, attention was 

 first turned to a method of immunizing cattle 

 against the disease. The Bureau of Animal In- 

 dustry and a number of experiment stations have 

 worked out a very successful method according 



