RECIPES, FORMUL AND USEFUL HINTS. 137 
Eosin and fuschine (aniline colors) are used in a two per cent. aque- 
ous solution but have a tendency to stain all parts equally. The method 
of operation is similar to that with carmine. 
Nitrate of silver is used for differentiating the walls of cells. The ob- 
ject is placed for a few moments in a solution made of nitrate of silver, 
one part, distilled water, 500 parts, then washed in distilled water and 
exposed to the direct rays of the sun. It is then mounted as may be 
desired and shows the cell walls black, and in many cases this is the 
only way in which they can be seen at all. 
Osmic acid, in one-tenth per cent. solution, is useful fo studying 
nerves and fatty tissues as it stains them black. Great care should be 
taken in using osmic acid asit is one of the most poisonous substances 
known, and its vapor badly affects the eyes and nasal passages. 
Chloride of gold is also of value in studying the histology of the 
nerves. Sections are first placed from five to seven minutes in a one 
half per cent. solution of the chloride, then soaked in distilled water 
several hours, next placed in water acidulated with lactic acid to reduce 
the chloride, and after the proper color (a dark purple) is obtained, the 
specimens are washed with distilled water and soaked in alcohol and 
mounted as may be desired. 
Moleschott’s acetic acid and alcohol (strong). 
Strong acetic acid (sp. gr. I. 070) I part. 
Strong alcohol I part. 
Distilled water 2 parts. 
This hardens many organs, makes connective tissue transparent and 
renders albumen distinct. 
Moleschott’s acetic acid (weak). 
Acetic acid (sp. gr. 1.070) I part. 
Alcohol 25 parts. 
Distilled water 50 parts. 
This is better for delicate tissues than the strong. Besides rendering 
connective tissue transparent, acetic acid renders the nuclei of cells 
more plainly visible. When a one per cent. solution of acetic acid is 
