246 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



gives a margin of a possible 2 per cent of error, and this small number 

 may be still further lessened by care in making the test. For prac- 

 tical purposes any animal that reacts must be considered tuberculous. 



Limitations of the Test. TEe test should not be applied to cows 

 that have just calved or are about to calve, as the temperature at this 

 time is apt to vary considerably from the normal. For this same rea- 

 son it should not be applied to any animal that is in a feverish con- 

 dition from any cause. 



The test fails to detect the presence of the disease in the animal 

 that is very recently infected. The disease has to make a little prog- 

 ress before the test reveals its presence, and in the beginning of each 

 case there is a period between the entrance of the germs into the body 

 and the time when they have multiplied sufficiently for the test to 

 reveal their presence. This is called the period of incubation and 

 lasts from ten days to two months. 



When the disease is far advanced and the animal is wasting, the 

 test sometimes fails to detect it. This is not of much practical im- 

 portance, as such cases can generally be recognized without the aid of 

 tuberculin. 



Protective Inoculation. For some years efforts have been made 

 to discover a method of rendering cattle immune to the disease in such 

 a way as men are protected from smallpox by vaccination. Up to the 

 present these efforts have been only partially successful, and until the 

 methods in use have been perfected by further investigations they can 

 not be recommended as of practical use in the suppression of tha 

 disease. 



Suppression of the Disease. The first step in getting rid of the 

 disease is to find out how many of the herd are affected by it. This 

 is done by applying the tuberculin test. This will show a larger or 

 smaller number of the herd to be affected, and the proper course to 

 pursue will depend largely upon the proportion of the reactors in it. 



Suppose that only a few cattle react, say 15 out of 100, or in that 

 proportion. In this case the reactors are first carefully examined, and 

 if any of them show symptoms of the disease by coughing, loss of 

 condition, or any other of the signs by which the disease is recognized 

 without the test, such animals should be slaughtered. 



The other reactors should then be entirely separated from the 

 healthy cattle. If possible they should be put in a separate building, 

 but if this can not be done a tight partition should be built between 

 the diseased and the healthy cattle and separate ventilation provided. 

 The person who attends to the reactors should not go near the healthy 

 animals, as he may carry the infection to them on his hands, clothes, 

 or boots. For the same reason the feeding and watering must be done 

 with separate utensils. 



When at pasture the reactors must not be put into a field where 

 they can reach across a fence to healthy cattle. Whenever a calf is 

 born among the reactors it should be immediately separated from its 

 mother and brought up by hand or on a healthy cow. The calf is 

 usually born healthy, but would soon catch the disease from its 

 mother if allowed to remain with her. 



