12 MANUAL OF MICROBIOLOGICAL METHODS 



factory. Even experienced workers sometimes discover to their dismay 

 that they took too much for granted as to the purity of their reagents, 

 cleanUness of sUdes and covers, or proper compounding of the staining 

 solutions. A technic should, therefore, be checked upon known organ- 

 isms as controls. It is, furthermore, important to know that the solutions 

 and water used for dilution are reasonably free from bacteria and spores. 



Staining Formulas 



There has always been a surprising amount of inaccuracy in the litera- 

 ture concerning staining solutions. This is due to a variety of causes: 

 indefiniteness in the original publication, mistakes of copying by later 

 authors, modifications of the original which are not described as modifica- 

 tions and come later to be ascribed to the original author, failure of 

 authors to cite references when giving their methods. For such reasons 

 it has proved necessary in this publication to give in many instances both 

 the original (rather indefinite) formula and an emended formula as 

 interpreted by the committee. The committee, however, assumes no 

 responsibility for the identity of the two and offers the emendation merely to 

 prevent the perpetuation of formulas which are clearly ambiguous or indefinite 

 as to their ingredients. Recent cooperation among this committee, the 

 Biological Stain Commission, and the National Formulary Committee of 

 the American Pharmaceutical Association has resulted in the virtual 

 adoption of these emended formulas. 



Staining schedule. Tap vs. distilled water. When washing slides after 

 applying any stain, tap water is ordinarily more convenient to use than 

 distilled water, and in the staining schedules that follow, tap water is 

 specified in those instances where its use is considered to be ordinarily 

 unobjectionable. It must be remembered, however, that the use of dis- 

 tilled water is never contraindicated for such purposes, and many bacteri- 

 ologists perfer it for all steps where washing is called for, because it is 

 not subject to variation in composition, buffer content, etc. 



GENERAL BACTERIAL STAINS— RECOMMENDED PROCEDURES^ 



ZiehVs Carbol-fuchsin 



Old statement of formula Emended statement of formula 



Solution A 



Sat ale sol basic fuchsin 10 ml Basic fuchsin (90 % dye content) 0.3 g 



5 % sol carbolic acid 100 ml Ethyl alcohol (95 %) 10 ml 



Solution B 



Phenol 5 g 



Distilled water 95 ml 



Mix solutions A and B 



1 In these discussions, small-size type is used for all formulas and directions for pre- 

 paring them, text-size type for all other directions concerning recommended pro- 

 cedures, and small-size type for similar matters concerning alternate procedures. 



