TUBERCULOSIS 



285 



but not into the deeper lying muscular tissue. Before the 

 syringe is used it should be sterilized by placing it in cold 

 water and bringing the water to the boiling-point. 



The dose of tuberculin varies, depending on the degree of 

 concentration. The usual strength employed requires 2 

 cubic centimeters to 1,000 pounds live weight. It is desir- 

 able that the animals tested shall be in a normal condition : 

 hence, the injection of the tuberculin should be preceded 



Hours After Injection. 



Fig. 50. Reaction Curves in the Tuberculin I <-t 



Curve 1 represents the temperature of a healthy animal after th<- injection of 



tuberculin. Curves 2 and 3 represent the temperatures of tubercular animals 



following the administration of tuberculin 



by a careful examination of each animal. Any animals 

 showing abnormal temperatures should not be injected. 

 The normal physiological functions, such as calving, oestrum, 

 or "heat," may or may not affect the temperature. Com- 

 plete notes should be made as to the condition of the ani- 

 mals, so that these facts may be considered in the interpre- 

 tation of the records. A negative reaction in the case of a 

 cow in heat or that has recently calved is as reliable as on 

 any animal, while a positive reaction may not be so reliable. 

 Since it takes a number of hours to produce the febrile 

 reaction in the case of an affected animal, it is not neces- 



