CONTAGIOUS DISEASES. 819 



ticks that infest the cattle in the South in large numbers. Southern native 

 cattle become immune to the disease, but Northern cattle taken South take 

 the disease and die. Southern cattle taken North, in warm weather, carry 

 the ticks wdth them, from which the disease spreads by their biting the 

 Northern cattle, or by the cattle eating the ticks that drop onto the grass, 

 or by eating the excrement of the ticks. Frost kills the ticks; on this 

 account it is considered sato to drive Southern cattle North during the 

 winter, but fatal to Northern cittle during the summer. Southern cattle 

 wintered in the North lose their immunity and then are susceptible to it, 

 the same as Northern cattle. On acco';.ii • of the tremendous losses from 

 this disease, the Western States have enc^Kied laws preventing Southern 

 cattle from being driven North, except durmg the winter, and Illinois 

 requires them to be shipped in special cars, into a special section of the 

 Union Stock Yards, and driven to slaughter through special roads to avoid 

 any danger of infecting Northern cattle that might be taken back to the 

 country as feeders. The mortality runs from VO per cent, upwards. 



It has long been desired to take fancy Northern bulls South to improve 

 the grade of Southern catcle, but until now it has been impossible to do so 

 on account of their almost certain death from Texas fever, but now (1898) 

 vaccination of such bulls, with an antitoxin got from the cultivation of the 

 germs of it, is being quite extensively used with good success. The anti- 

 toxin can be got from most of the Agricultural Experimental Stations, with 

 directions how to use it. 



Incubation. — The stage of incubation is from seven to thirty-five daySo 

 The blood undergoes a material change, and some of its elements escape 

 into the various tissues of the body and into the urine, giving the latter a 

 bloody appearance. 



How to know it. — As in pleuro-pneumonia, a marked symptom is an 

 increase of heat, to 104° to 106°; the pulse rises from 40 beats a minute 

 (the average for healthy steers) up to 120 a minute. The fever is generally 

 preceded by a chill; the dung and urine become scanty, high colored, or 

 bloody; the milk fails rapidly; yellow matter is discharged from the nos- 

 trils and mouth; the animal assumes a peculiarly dejected look; the back 

 is arched; the flanks become hollow; the gait unsteady or staggering, and 

 the hair rough; the cough is more or less frequent; the urine coagulates on 

 boiling; the mucous membranes are deep yellow or brown color, and that 

 of the rectum dark red. There is but little trace of disease in the first 

 thi-ee stomachs, but the fourth stomach shows congestion, and the intestines 

 are still more gorged and blood-stained. The liver is not seriously affected, 

 but the gall bladder is filled with thick, dark colored bile; the kidneys are 

 also congested, and the secretion in the bladder is bloody or blood-stained; 



