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tilled water is made. Before using these solutions 

 they are mixed, i cc. of each being taken, and the 

 mixture diluted so as to make a liter. The mixture 

 can be made only at the moment when it is to be 

 employed ; otherwise metallic silver is precipitated 

 by the light. 



This reagent colors living protoplasm black, 

 while dead protoplasm remains uncolored. The 

 reaction may be obtained with a solution diluted 

 very greatly (even i : i, 000,000).' 



Tannic acid also gives a reaction, but this 

 is effected only with a less dilute solution 

 (i : 10,000). 



Glucose gives a reaction with a solution of 

 i : 100,000, the cells coloring brown, and not black. 

 In this proportion, therefore, nitrate of silver is an 

 excellent reagent for this sugar. 



1 These very dilute solutions cannot be employed in as small quantity 

 as micro-chemical reagents usually are. To obtain good results it is neces- 

 sary, according to Bokorny, to immerse a few cells (e. g. of Spirogyra) in a 

 large quantity (.5 i liter) of the reagent for six to twelve hours. 

 French Translator. 



