STAINING OF SECTIONS 121 



4. Wash in several changes of absolute alcohol until violet color 

 is no longer given off. 



5. Clear in xylol and mount in Canada balsam. 

 Gram-Weigert Method for Celloidin Sections. In this, as in the 



preceding paraffin section method, the tissue should have received 

 a preliminary stain in carmin. If not stained in bulk, the sections 

 themselves should be left in the alum carmin over night. 



1. Fasten the celloidin section on slide with ether vapor and stain 

 for twenty minutes with anilin-water gentian violet. 



2. Wash in normal salt solution. 



3. Leave one minute in the iodin solution (solution the same as 

 in preceding method). 



4. Wash off in water. 



5. Dry with filter paper to remove as much moisture as possible. 



6. Wash in several changes of anilin oil to remove most of the 

 voilet stain. 



7. Clear with several changes of xylol. Examine with the micro- 

 scope before mounting in Canada balsam to see whether enough of 

 the violet stain has been removed. If not, wash again in anilin oil, 

 then in xylol. 



8. Finally, mount in Canada balsam. 



Levaditti Silvering Method for Exhibiting Spirochetce, particularly 

 Spirochetce pallida in Tissues in Congenital Syphilis. This is an 

 impregnation method to impregnate microorganisms in tissues with 

 metallic silver. Although not a staining method, it should be con- 

 sidered here. The steps are as follows: 



1. Fix small pieces of tissue in a solution of formalin 1 part, water 

 3 parts (10 per cent, formalin solution) for twenty-four hours. 



2. In 95 per cent, alcohol for twenty-four hours. 



3. Wash in distilled water. 



4. Place in a 1^ per cent, solution of nitrate of silver in a dark 

 bottle to protect against light; keep in the incubator for three days. 



5. Wash in distilled water. 



6. Place in the following reducing solution (keep in light and at 

 room temperature): 



Pyrogallic acid 2 grams 



Formalin . . . . . . 5 c.c. 



Distilled water 100 c.c. 



7. Wash in distilled water. 



8. Embed in celloidin or paraffin. 



9. Dehydrate sections, clear in xylol, and without staining mount 

 in Canada balsam. 



The spirochetae appear perfectly black on a yellowish background. 



