LABORATORY DIAGNOSIS 6g 



from four to six parts of sputum caccording to the con- 

 sistence of the latter. The resulting mixture is shaken 

 well and allowed to stand for two or three hours till 

 solution occurs, which may be hastened by placing the 

 mixture in the incubator. On centrifuging, the tubercle 

 bacilli are obtained concentrated in the sediment, which 

 is generally very slight. Other acid-fast organisms are 

 occasionally met with (p. 74) in sputum. Negative 

 evidence is only of value when repeated examinations 

 have been made. 



Milk. See p. 222. 



Urine. To exclude the smegma bacillus (pp. 61, 73), 

 the urine may be drawn off with a catheter. The urine 

 should bo allowed to stand in a conical glass for twenty- 

 four hours, or should be centrifuged. (Russ's electrical 

 method (p. 10) often reveals the presence of tubercle 

 bacilli when centrifugal methods fail to do so.) Should a 

 catheter not be used, the meatus urinarius and the labia 

 (or glans penis) should be cleansed by sponging. The 

 first portion of urine should be discarded. The film is 

 stained as for sputum, but after the acid treatment is 

 put in absolute alcohol for one minute (or, after staining, is 

 put in alcohol containing 3 per cent, hydrochloric acid for 

 ten minutes Housell's method) to decolorise any smegma 

 bacilli, washed in water and counter-stained. Inoculation 

 of guinea-pigs may also be used. 



Agglutination Reaction. The serum of tuberculous 

 cases agglutinates the tubercle bacillus, but the technique 

 is difficult. Special cultures of the tubercle bacillus have 

 to be employed, or dried and triturated cultures may be 

 used (Koch). 



Tuberculin Reaction. See p. 67. 



Von Pirquefs Cutaneous Reaction consists in the appli- 

 cation of tuberculin to a scarified surface. In twenty- 

 four hours red papules arise. It gives positive results in 

 healed cases of adults as well as in those where the disease 

 is active. It has more significance with children under 

 three years. Lapage says the method gives a lower 

 percentage of results than the subcutaneous, and that a 

 single negative result is not of much value. Lapage's 

 statistics on this method show that at the end of the school 

 age between 50 and 60 per cent, of children have become 

 infected with tuberculosis. 



