STAINING OF SECTIONS 731 



The spirochsetes stain black, and stand out prominently against the deep 

 yellow colour of the tissues. 



Levaditi's methods. In order to avoid the deposits which are often formed 

 when Bertarelli's method is used, Levaditi stained the tissue in bulk in the 

 silver solution. Levaditi has described two methods, the second of which 

 gives the better results. 



First method. 1. Fix a small piece of tissue in 10 per cent, formalin for 

 24 hours. 



2. Harden in absolute alcohol for 24 hours. 



3. Wash in distilled water for 5 minutes. 



4. Immerse the tissue in a solution of silver nitrate in a ground-glass 

 stoppered bottle and keep it in the dark for 3 days at a temperature of 38 C. 



Crystals of silver nitrate, - 1 '50 grams. 



Distilled water, .... - 100 c.c. 



5. Wash in water. Then immerse for 24 hours at the temperature of the 

 laboratory in the following solution : 



Pyrogallol, 4 grams. 



Formalin, 5 c.c. 



Distilled water, - 100 



6. Wash in distilled water. 



7. Dehydrate in 80 per cent, alcohol, then in absolute alcohol, clear in xylol 

 and embed in paraffin. 



8. Cut and mount the sections carefully (p. 215) and stain them on the 

 slide for 10 minutes with Giemsa's solution undiluted. 



9. Wash in water and differentiate in absolute alcohol to which a few drops 

 of clove oil have been added. 



10. Wash in absolute alcohol, oil of bergamot and xylol and mount in 

 balsam. 



The re-staining of the groundwork with Giemsa's solution (Stage 8) is not essential ; 

 it is better to omit it. 

 Second method (Levaditi and Manouelian). Recommended. This method 



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FIG. 348. Treponema pallidum. Section of lung. Silver impregnation method. 

 (Oc. 2, obj. T Uh, Zeiss.) 



differs from the preceding in the introduction of pyridine which shortens the 

 time of staining and facilitates the reduction of the silver salt. 



