Staining 659 



Nearly all of the recent methods of staining are based upon 

 the impenetrability of the bacillary substance by mineral acids which 

 characterizes the acid-fast or acid-proof (saurefest) micro-organisms. 

 But it is not improbable that we have been led into error by the 

 assumption, upon inadequate grounds, that this is a constant and 

 uniform quality of the tubercle bacillus and similar micro-organisms. 

 The interesting observations of Much* have shown that many of 

 the paradoxes of tuberculosis can be accounted for by the fact that 

 during certain stages, or under certain conditions, the bacilli are not 

 acid-proof at all. Thus, caseous masses from the lungs of cattle 

 show complete absence of tubercle bacilli when examined by 

 the usual method, yet cause tj^ical tuberculosis when implanted 

 into guinea-pigs, with t5^ical bacilli, recoverable upon culture- 

 media, in the lesions. This is certainly due to the inability of the 

 bacilli in the bovine lesions mentioned to endure the acids, for 

 when the same tissues are stained by Gram's method many organ- 

 isms can be found. This shows that Gram's method is really a 

 more useful method for demonstrating the bacillus than those in 

 which acids are employed. Much has found two forms of the 

 tubercle bacillus, one rod-like, the other granular, that are not 

 acid-proof, and has succeeded in changing one into the other by 

 experimental manipulation. ' He believes that the acid-proof con- 

 dition has some bearing upon virulence, and speculates that the 

 more acid-proof the organisms are, the less virulent they will be 

 found. 



In this connection the work of Maher,t who claims to be able, 

 by appropriate methods of cultivation, to make many of the ordi- 

 nary saprophytic bacteria (Bacillus coli, B. subtiUs, etc.) thor- 

 oughly acid-proof, must be mentioned. 



In all cases where the detection of tubercle bacilli in pus or secre- 

 tions is a matter of clinical importance, it must be remembered that 

 the quantity of material examined by the staining method is ex- 

 tremely small, so that a few bacilli in a relatively large quantity of 

 matter can easily escape discovery. 



As the purpose for which the staining is most frequently performed 

 is the differential diagnosis of the disease through the demonstra- 

 tion of the bacilli in sputum, the method by which this can be 

 accomplished will be first described. 



Staining the Bacillus in Sputum. — When the sputum is muco- 

 purulent and nummular, any portion of it may suffice for ex- 

 amination, but if the patient be in the early stages of tuberculosis, 

 and the sputum is chiefly thin, seromucus, and flocculent, care must 

 be exercised to see that such portion of it as is most likely to contain 

 the micro-organisms be examined. 



If one desires to make a very careful examination, it is well to 



* "Berliner klin. Wochenschrift," April 6, 1908, p. 691. 



t" International Conference on Tuberculosis," Philadelphia, 1907. 



