Monthly Microscoplcan 
Journal, Feb. 1, 1869. J 
Royal Microsco]pical Society. 
103 
these results may be attained by making use of a solution of bicblo- 
ride of palladium, which gives to the tissue a rich brownish-black 
colour. This should be used in the strength of one part of palladium 
to five hundred of water, and the specimen need only remain in 
this solution for ten minutes; it may then be removed, washed 
in the same way with acidulated water, and transferred to the 
capsule containing the formic acid and spirit. In a warm place, 
the reduction of the palladium and staining of the tissue is com- 
plete in about a quarter of an hour. Both these methods are 
applicable for sections of brain and spinal cord, or of any other 
organ.^ 
There is a method of double tinting also, with silver *and gold, 
which I occasionally employ, and which yields beautiful results 
with sections of the kidney. The section, if taken from an organ 
hardened in chromic acid, requires to be first soaked for a time in 
water, in order to get rid of all this acid — and this is more rapidly 
brought about if the water be somewhat warm. Then it is placed 
in a solution of nitrate of silver (1 : 600) for five or ten minutes ; 
taken from this, washed in pure water for a minute, and thence 
transferred to the acidulated gold solution as before. After the 
reduction of the gold by formic acid, the specimen may be mounted 
in the solution of Canada balsam in benzole, and then exposed to 
light, in order to bring about the complete reduction of the silver. 
When this has been done, it will be found oil microscopical exa- 
mination, that the epithelial elements are for the most part stained of 
a brownish-black colour by the reduced silver, whilst the intervening 
fibrous tissue elements and the walls of the vessels are stained purple 
by the reduced gold. The two kinds of tissue elements seem to 
exercise a sort of elective affinity for the different metals. 
I bring these forward as additional methods of tinting, rather 
than because they possess any decided advantages over the more 
ordinarily employed carmine process. 
