STAINING 207 



The sulphuric acid in Gabbet's blue removes the carbol- 

 fuchsin from everything except the "acid-fast" bacteria, 

 which remain red, and the blue stains the decolorized bac- 

 teria and nuclei of any tissue cells present. 



Ziehl-Neebon method: 

 1, 2, 3, as in Gabbet's method. 



4. Decolorize with 10 per cent HCl until washing with 



water shows only a faint pink color left on sHde. 



5. Wash thoroughly. 



6. Stain with Loffler's blue one or two minutes. 



7. Wash, dry and examine. 



The results are the same as with Gabbet's method. 



Staining of Capsules. Rdbiger's Method.— Films of the 

 organism to show capsules should be freshly prepared, dried 

 but not fixed. Material is usually obtained from milk or 

 blood. A drop of the fluid is placed on the middle of a slide 

 about one-fourth of the distance from one end. The nar- 

 row edge of another clean slide is placed in this drop and then 

 drawn lengthwise across the slide with firm pressure. This 

 gives a thin layer which is necessary if good results are to be 

 expected. The preparation is covered with a freshly pre- 

 pared saturated solution of gentian violet in formalin and 

 this is allowed to stain for thirty seconds. Then wash lightly, 

 dry and examine. The organisms appear deeply violet and 

 much larger than with ordinary stains and capsules are well 

 stained and show^ well. 



Welch's Method.— Vrepsire films as in the above method. 

 Immediately after the film is prepared cover with glacial 

 acetic acid for ten to twenty seconds. Wash off the acid 

 with carbol-fuchsin. Wash the stain oft' with physiological 

 normal salt solution (0.85 per cent) until all surplus stain is 

 removed. Dry and examine. Capsules and bacteria are red. 



Staining of Flagella.— The rendering of flagella visible is 

 considered one of the most difficult processes in staining. 

 Experience of a number of years, during which whole classes 

 numbering from 100 to 300 students accomplish this result, 

 shows that it is no more difficult than many other staining 

 processes. The essentials are: (1) clean slides, (2) young 

 cultures on agar slopes, (3) freshly prepared mordant and 



