172 Tue Microscope. 
also stains the intercellular substance of cartilage and the cor- 
nea. <A one per cent. solution is kept in stock, and this is 
diluted to one-half or one-fourth per cent. when required for 
use. It should be kept in a dark place, or in a bottle covered 
completely with black paper. 
The tissue to be stained must be as fresh as possible. It 
is first thoroughly washed in distilled water to remove any 
chlorides that may be present. It is then placed in a one-half 
or one-fourth per cent. solution of the staining for five or ten 
minutes, or until it has a milky or whitish appearance. It is 
now again thoroughly washed in water, to remove all traces of 
the silver except that which has been taken up by the cement 
substance. After exposing this tissue, which has been placed 
in fresh water, to diffuse daylight it will assume a slightly 
brown color, owing to the decomposition of the absorbed stain- 
ing into the black oxide of silver. 
A membrane that has been stained by this method will ex- 
hibit what are known as “ silver lines,” a fine black line run- 
ning between the cells and separating one from another. 
After staining with the silver the tissue may be stained 
with hematoxylin and mounted in glycerine or glycerine jelly, 
only it is necessary that the slide be kept from the light if it be 
desired to have the preparation retain its first clearness. 
CHLORIDE OF GOLD. 
A two per cent. solution is made and reduced as occasion 
requires, to the desired strength. It is kept in a black bottle or 
in a dark place, like the silver solution. 
There are several methods used for demonstrating tissues 
with gold solutions, as “*Conheim’s method,” “ Pritchard’s 
method,” etc. They all depend upon some acid, or upon day- 
light, to reduce the gold. Cole recommends that the tissue be 
placed in a watch gless and the juice of a fresh lemon squeezed 
over it, in which the tissue is allowed to remain for five or ten 
minutes. It is then washed in distilled water, to remove all the 
juice, and placed in a one-half or one per cent. solution of the 
gold for thirty minutes. The surplus gold is washed away, and 
the tissue is placed in a mixture of one part of formic acid 
and three parts of water for twenty-four hours, in a cool place, 
and away from the light. The gold chloride will then be re- 
