3 
fact that the most beautiful and well-defined structures may 
be rendered quite invisible by being soaked in aqueous solu- 
tion of bichromate of potash for three days, one day in car- 
mine solution, and then in caustic soda ! 
In order that I may not express myself against the mode of 
preparation followed by this and many other observers in 
Germany in the present day more strongly than is justified 
by the results obtained as shown by their own drawings, I 
■would refer to Hartmann’s figure. Of this drawing it is 
not too much to say that it represents nothing sufficiently 
definite to enable any one to form an idea of the structure of 
the part. The drawing, and I conclude the preparation from 
which it was taken, are far behind the day ; and it seems to 
me most remarkable that after all the anatomical research of 
the last twenty years an observer should publish such a figure 
as this as a representation of natural structure. The nerve- 
fibres are completely altered by the mode of investigation 
followed, and the finer fibres are of course destroyed or 
rendered invisible. Nor can I admit that the epithelium 
upon the summit of the papillae represented in his fig. 64 
gives a correct idea of this structure. 
Unfortunately, Engelmann, who is the last writer on the 
subject, does not appear to have seen my paper, which was pub- 
lished three years before his own memoir. He, however, con- 
firms some of my observations, but has evidently failed to see 
the numerous nuclei connected with the subdivisions of the 
nerve-fibres, and represented in my figures 1, 2, and 3. 
That remarkable and intricate plexus of the very finest 
nerve-fibres which I have described and figured has also 
escaped his observation. But it would have been impossible 
for him to demonstrate these and many other points by the 
process of investigation which he followed, while the papillae 
of the Rana temporaria are not at all well adapted for study- 
ing the finest ramifications of the nerve-fibres. 
It may be proved conclusively by experiments that soaking 
delicate animal tissues in dilute aqueous solution of bichro- 
mate of potash renders invisible and destrojs structures 
which can be demonstrated by other means. Iuquiries con- 
ducted by the aid of such plans of preparation retard rather 
than advance anatomical inquiry, for some of the most im- 
portant anatomical characters are rendered completely invi- 
sible. The very conflicting opinions now entertained by 
observers in Germany upon the structure of these papillte, 
render it important that they should be studied again with, 
the advantage of the highest powers and the most advan- 
tageous methods of preparation which we now possess. 
