314 APPENDIX 



4. A saturated solution of potassium acetate. This is 

 sometimes used as a permanent mount for nerve fibres stained 

 with osmic acid. The edges of the cover-slip may be surrounded 

 with soluble glass. 



5. Dilute Glycerine. 1 part of glycerine, 2 parts of water 

 and a drop or two of camphor water or salicylic acid. Or equal 

 parts of glycerine and water. Or alcohol in place of the water. 



6. Glycerine-jelly. 



Glycerine 70 c.c. 



Water 60 c.c. 



Gelatine lOgrms. 



Place the gelatine with the water in a porcelain capsule, heat 

 the mixture in a small water- bath over a Bunsen burner until 

 the gelatine is dissolved, stirring the while and taking care that 

 the gelatine does not stick to the capsule. The water should 

 not be allowed to boil, or at any rate for a short time only. To 

 the hot solution add the glycerine and a drop or two of a strong 

 alcoholic solution of thymol. If necessary, cool the mixture to 

 about 40 C., add the beaten-up white of an egg and well mix. 

 Then heat as before to about 90 C., stirring continuously. .Filter 

 through a hot- water filter. 



The gelatine may be left for a day in the cold water to swell 

 up, then dissolved by warming to about 40 C. The glycerine, 

 warmed to about the same temperature, is added. Then proceed 

 as above. 



7. Glycerine. Should be neutral, acidity may commonly 

 be detected by the taste. It is apt to become dilute by taking 

 up water from the air. Delicate sections should be soaked in 

 dilute glycerine before being placed in strong glycerine. 



Many gold chloride and carmine stained sections are advan- 

 tageously mounted in glycerine containing 1 p.c. of formic acid 

 1-16 sp. gr. 



When sections are mounted in dilute glycerine or in glycerine, 

 the edges of the cover- slip are perhaps best cemented to the slide 

 with gold size ; they may first be surrounded with a thin film of 

 hot glycerine-jelly, and this allowed to dry (cp. p. 40, 6, 7). 



