70 STUDY AND IDENTIFICATION OF BACTERIA. 



salt solution with 1/4% of lysol. Each c.c. contains i/io mg. One 

 c.c. of this stock solution added to 99 c.c. of salt solution, with 1/4% 

 of lysol, would give a working solution, each c.c. of which would 

 contain i/iooo mg. of tuberculin. 



For diagnostic reactions we have, besides the method of injecting 

 tuberculin and noting presence or absence of fever, four more recent 

 diagnostic tuberculin tests : (i) Variations in opsonic index. (2) 

 Instillation into one eye of a drop of 1/2% or i% -solution of purified 

 tuberculin. Reaction is shown by redness, especially of inner canthus, 

 in 12 to 24 hours (Calmette). (3) The cutaneous inoculation 

 method similar to ordinary vaccination methods. The appearance of 

 bright red papules in 24 hours indicates reaction (von Pirquet). 

 (4) Ointment tuberculin test. Rub in 50% ointment of tuberculin in 

 lanolin. Reaction is shown by dermatitis with reddened papules in 

 24 to 48 hours. (5) Inoculation of bovine and human tuberculin to 

 diagnose type of infection (Detre). 



In staining it is better to use the Ziehl-Neelsen method, decolor- 

 izing with 3% hydrochloric acid in 95% alcohol. The alcohol, for all 

 practical purposes, enables us to eliminate the smegma and similar 

 bacilli, these being decolorized by such treatment. There are two 

 objections to the Gabbett method, where decolorizer and counter- 

 stain are combined: (i) We cannot judge of the degree of decolor- 

 ization we are working in the dark; and (2) the matter of elimination 

 of smegma bacilli is impossible. 



Pappenheim's method, in which corallin and methylene blue are 

 dissolved in alcohol, does not appear to have any advantage over acid 

 alcohol. As a practical point when the question of tuberculosis of 

 the genito-urinary tract is involved, inoculate a guinea-pig with 

 urinary sediment. 



It must be remembered that in young cultures of tubercle bacilli 

 many of the rods are nonacid-fast, taking the blue of the counter- 

 stain, while older rods are acid-fast. This frequently causes suspicion 

 of a contaminated culture. 



Bacillus Leprae (Hansen, 1874). This is the cause of leprosy. 

 In nodular leprosy the organism is readily and in the greatest abun- 

 dance found in the juice of the tubercles of the skin, nasal and pharyn- 



