324 Transactions of the Society. 



of tissue not more than 5 mm. in thickness, I have obtained 

 satisfactory impregnations of the Golgi apparatus after one to one- 

 and-a-half hour's reduction. By increasing the time the impreg- 

 nation was not affected in any way. It would seem therefore that 

 the developer penetrates rapidly. The pale yellow colour of the 

 reducing fluid when fresh is apt to change after a few weeks to a 

 dark brown. In spite of this it is still efficacious, though somewhat 

 slower in action. 



Toning. — Usually the ground cytoplasm of cells is pale yellow 

 in the untoned sections. If desired they may be toned until grey, 

 usually in about ten minutes by the use of the solutions described 

 above, which should be kept in separate bottles and only mixed 

 before use. The most economical method is to pour a few c.cm. 

 over the slides. The fluid may be poured into a small test tube 

 after use and used several times over. Once the gold precipitates 

 (as usually happens after several days) it should be thrown away. 



Elimination of Precijntate. — Veratti has recommended the 

 following procedure for eliminating silver precipitate from 

 sections : — 



1. Wash sections on the slide in Aq. dest. 



2. Dip for a few seconds into — 



Potassium permanganate . . . ■ 5 grm. 

 Sulphuric acid ..... 1 c.cm. 



Aq. dest. ...... 1000 „ 



3. Dip into a 1 p.c. solution of oxalic acid for a few seconds. 



4. Wash in distilled water. Examine with the microscope; 

 if precipitate is not yet removed repeat the process. 



Although this method will remove deposit from the tissues, it 

 also discolorizes the Golgi apparatus and any other impregnated 

 elements. In my hands it has always failed to correct an over- 

 impregnated preparation. 



Counterstaining the sections after toning is often useful. 

 Most of the common histological stains may be used without 

 affecting the impregnation. But the selectivity of dyes is usually 

 diminished. Nevertheless the following have given me satisfactory 

 results: — (1) Ehrlich's haematoxylin and eosin; (2) toluidin blue 

 eosin ; (3) Mann's methyl blue eosin ; (4) pyronin methyl green ; 

 (5) safranin. Of these 1, 3 and 4 (this latter especially) give fairly 

 accurate pictures of the basophility and oxy'phility of cell-elements. 

 For general use safranin used as follows has given me the best 

 results : — 



1. Sections on the slide are brought into a saturated solution of 

 safranin (Griibler) in equal parts of absolute alcohol and aniline 

 oil- water. They are left in this for from fifteen minutes to several 

 hours. 



2. Einse in water. 



