380 TUBERCULOSIS 



containing 0-5 per cent, carbolic acid or lysol, and kept in sealed 

 " ampoules," each containing i c.c. A convenient method to 

 adopt is to take 99 c.c. of diluent and add the whole of a i c.c. 

 bottle of tuberculin. Each cubic centimetre of this contains i o milli- 

 grammes of fluid, or yj^ c.c. ; several ampoules are prepared, and the 

 remainder of the fluid diluted with an equal amount of the diluent. 

 Each cubic centimetre now contains 5 milligrammes, or -^^ c.c., and 

 several ampoules are filled with this dilution. Lastly, what remains, 

 or part of it, is diluted with four times its volume of diluent, so that 

 each cubic centimetre contains i milligramme, or yoVo" c - c> > f tuber- 

 culin. It will be noted that the fraction of a milligramme refers to the 

 tuberculin as sold, and not to any active constituent it is supposed to 

 contain. It is recommended to err on the side of caution, and to com- 

 mence with j-^Vo" c - c -> an d then to go on to -^~ and finally T ^Q-; but 

 with proper selection of cases it is probable that the risk with -^^ is 

 infinitesimal. The rise in temperature which constitutes a reaction 

 should be at least i F., and is usually more. It usually com- 

 mences in eight to twelve hours, rises for another two hours, 

 remains up for a few hours longer, and then falls rapidly. There 

 is often a considerable amount of general malaise. 



It should be used only in cases in which the diagnosis cannot 

 be made by other methods with ease and certainty, and in which 

 it is of great importance that it should be made definitely and 

 rapidly. Thus, a patient living under favourable conditions who 

 developed ambiguous indications of phthisis might fairly be 

 watched for a time, his weight recorded, an attempt made to 

 obtain sputum, etc. But the same signs occurring in a person 

 who was about to get married, or a medical man thinking of 

 taking a resident appointment in a hospital, would be a strong 

 indication for the diagnostic use of tuberculin. Perhaps its main 

 value is that it enables a negative diagnosis to be made with some 

 degree of confidence, and is the only agent which will do so. No 

 reaction after two injections of yj^ c.c. may be taken as definite 

 proof that the disease is absent. 



It should not be used (i) when the temperature is irregular 

 obviously, since the rise might not be due to the tuberculin and 

 (2) when there are secondary infections. 



Some cases of syphilis, leprosy, and actinomycosis are said to 

 react, but this is unusual, and the concomitant presence of tubercle 

 has not always been ruled out. 



In cattle the doses are larger. The tuberculin is usually diluted 



