Moiitlily Microscoi)icari 
Journal, Feb. 1, 1869. J 
lioyal Microscopical Society. 
95 
tissue, introduced by Lockhart Clarke, and which has done such 
admirable service in its day, is by any means a compUcated one ; 
but still, to ensure good results it does require a certain amount of 
practice on the part of the operator, and even though we attain to 
the utmost degree of skill, the mounting by this method will occupy 
about three times as long a period as when one of my equivalent 
methods is employed. 
I have not been satisfied with glycerine alone as a preservative 
medium, because, although yielding for a time such excellent results, 
the specimens so mounted will not retain their characteristic 
appearances indefinitely. After some time delicate specimens pre- 
served in this way are apt to become more or less granular in some 
parts and too transparent in others. What we want is a method 
or methods which will preserve specimens for any number of years 
without change. 
I will first speak of the methods which I have found the best 
for mounting specimens of liver, kidney, spleen, lung, &c. ; then 
of those which I employ for the mounting of sections of brain or 
spinal cord ; and lastly I will give some directions for the tinting 
of sections with chloride of gold and other metallic preparations. 
The Mounting of Sections of Liver, Kidney , &c. — About ten 
months ago I cut specimens from the same portion of a kidney 
which had been hardened in chromic acid,* and mounted them, 
without previous tinting of any kind, in about thirty different 
ways, so that, by comparing these specimens carefully with one 
another, I have now been able to ascertain what are the best 
methods for preserving all the characteristics of the tissues, and 
what methods are to be avoided on account of their tendency to 
render the sections too transparent — thereby obliterating their finer 
details. I will first speak of the various methods for mounting 
sections in balsams or in gum-resins. 
I have employed gum-dammara and Canada balsam in solvents 
of different kinds, having previously found that gum-mastic did not 
answer so well as either of the preceding. The solvents tried with 
each were chloroform, tetrachloride of carbon, ether, benzole, and 
the common commercial benzine, which is simply a less highly 
rectified product than the former. So far as the choice lies be- 
tween gum-dammara and Canada balsam, it is not a very important 
* As a general rule I use the chromic acid solution in the strength of one of the 
acid to three hundred of water. There is often an advantage, however, in placing 
the part to be hardened in a solution of bichromate of potash for the first week or 
ten days (ten grains of the salt to an ounce of water), the solution being renewed 
two or three times during this period. The solution of the bichromate has a much 
greater penetrative power than that of chromic acid. 
Of late a saturated solution of Picric Acid has been recommended for harden- 
ing tissues by Ranvier (see an early number of the new ' Journal de Physiolog. et 
Patholog.') ; but I cannot speak at all positively as to its advantages or disad- 
vantages, since I have scarcely given it a fair trial as yet. 
