THE TUBERCULIN TEST. 157 



being materially affected by the test. Similar experiments have 

 been made elsewhere, the results agreeing very closely with this 

 general statement. It is undoubtedly possible for cattle to be so 

 roughly handled during test that the milk flow might be seriously 

 affected, but this cannot be charged to the tuberculin. In cases 

 where serious results accompany or follow tuberculin tests, the 

 disturbance can usually be traced to some cause other than tuber- 

 culin. 



Accuracy. — Averages of very large numbers of animals 

 tested show that tuberculin has had an average accuracy in diag- 

 nosis of over 90 per cent, and in the hands of many veterinarians 

 who have been very careful in their work, it has been almost 

 infallible. Very advanced cases sometimes, although rarely, fail 

 to react. Such cases are easily detected by ordinary symptoms, 

 as a rule. 



The test. — Any number up to 60 or 70 may be included in 

 one test. Larger numbers can only be handled to advantage by 

 one who is thoroughly familiar with the test and who can use a 

 number of thermometers. 



The injection is made on the neck just in front of the shoul- 

 der or else just back of and a little above the elbow. 



At least two assistants are needed : one to hold a lantern and 

 assist in managing the cattle, another to hold some sort of a tray, 

 usually a short piece of board, for carrying the needed materials. 

 There will be needed an ordinary tumbler with a good layer of 

 cotton or oakum on the bottom and filled with 4 per cent carbolic 

 solution ; a one dram graduate, measured also for c. c.'s ; a vet- 

 erinary hypodermic syringe, holding 3 to 5 c. c, and provided 

 with several short and reasonably strong needles. The syringe 

 rinsed out with the carbolic solution occasionally. 

 is carried in the carbolic solution, except when in use, and may be 



If the operator is without sufficient help, a bicycle lantern can 

 be held in one hand while making the injection with the other. 

 By raising the skin with the thumb and first two fingers, a sort 

 of pocket can be made into which the needle can be thrust with 

 considerable force without penetrating deeply into the muscle. 

 The needle should be inserted by a quick stab, entering at right 

 angles to the skin surface. It is usually advisable for the operator 

 to stand well forward by the cow's shoulder. Some cattle are 



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