SHERWOOD: ON DIFFERENTIAL STAINING METHODS. 33 



considered not injurious to acid-fast tubercle bacilli/'"* and since 

 the patients are not positively tuberculous clinically, it would 

 appear that the organisms were probably saprophytes. The ac- 

 tion of the organisms towards Fonte's method was a border-line 

 one. In view of the work of Spengler'^ and also of Much^^ on 

 non-acid-fast tubercle bacilli, one can not use this border-line 

 reaction as evidence one way or the other. 



It is hoped to continue this work and determine the relative 

 frequency of occurrence of saprophytic acid-fast organisms in 

 urine and sputums and to further check up the value of Fonte's 

 and other promising methods of differentiation. If non-acid-fast 

 or partially acid-fast tubercle bacilli were very commonly met 

 with in urines and sputums from tuberculous patients it would be 

 quite evident that no staining method based upon acid -fastness 

 would be efficient, but there has not been much evidence brought 

 forward to show anytbirg but the scarcity of these non-acid-fast 

 strains. The work of Wherry^^ indicates that this cause of acid- 

 proofness of parasitic organisms is different from that of sapro- 

 phytes. As to the acid-fast properties of intermediate organisms 

 with a very low grade of virulence nothing has been reported 

 along the line of Wheriy's investigation. The many conflicting 

 results which have led to the development of so many differential 

 staining methods, added to conflicting opinions of the acid-proof- 

 ness of different members of this group, suggests a wide variation 

 in acid-proofness among the saprophytic members of the acid-fast 

 group, at least. The work of this paper further confirms this fact. 

 An explanation for the decolorization by Fonte's method of pure 

 cultures of the tubercle bacillus, as well as other acid-fast organ- 

 isms as reported in this paper, is that the tubercle bacillus, as well 

 as the others, was growing saprophytically, hence its acid-proof- 

 ness differed materially from that of the parasitic tubercle bacilli 

 of the twenty-nine positive clinical cases of tuberculosis. These 

 laboratory strains of the tubercle bacillus have also lost their 

 pathogenicity. It may be that the groups are so closely re- 

 lated as to offer insurmountable obstacles to their absolute and 

 complete differentiation. A method having a very high percent- 

 age of efficiency would be very valuable and desirable. 



3— Sci. Bui. X. 



