Tue Microscope. 5 
METHODS OF STUDY. 
FOURTH NUMBER, 
ALBERT E. JENKINS, ANN ARBOR, MICH. 
STAINING. 
2 the ever increasing activity of microscopical research, the 
subject of staining receives more general attention than any 
other step in the preparation of specimens, but until recently 
this study has been entirely empirical. As a consequence, 
staining has by many been regarded as an end in itself, and in 
the effort for variety and something new, both the mineral and 
vegetable kingdoms have been ransacked for unusual and strik- 
ing colors. But while to some a specimen may have a possible 
esthetic value from a combination of bright tints, it should al- 
Ways be remembered that the tingeing of sections is a power- 
ful means of analysis, making distinct differences in structure 
and composition, and rendering visible much that otherwise 
could not be seen at all. In view of this it may be written that 
the need now is not new dyes so much as careful and accurate 
tests of the action of those already known, and how they may 
be influenced and made more serviceable by use in connection 
with other reagents, especially those which will increase the 
selective power of the stain and render it more permanent. 
Since Hartig (1854) and Gerlach (1858) first employed car- 
mine in histological technology, it has been noticed that the 
different elements of tissues and cells would take only certain 
colors, or that they would retain them with varying degrees of 
resistance when subjected to further treatment. This election 
or determinance of color for known elements is the foundation 
of all staining processes, and is equivalent in value to chemical 
reaction, to which indeed it is akin. 
As to how a dye stains there is at present much discussion 
in learned circles. Formerly it was believed that the coloration 
was due toa simple absorption of the dye-stuff, but while this is 
undoubtedly true in some instances, it falls far short of explain- 
ing many of the complicated processes of modern microscopical 
technics. Recent investigators have very generally attributed 
the phenomena to chemical action, the formation of new and defi- 
nite compounds from the substance of the tissue and the dye- 
