1881.] . Microscopy. 259 
mounted is diluted glycerine; and no pressure is allowed to act 
upon the specimens other than that which the thin cover-glass 
exerts when of the embedding fluid so much is removed by blot- 
ting paper that it just fills out the empty space between the slide 
and the cover. Thus the margin only of the specimen comes 
in contact with the fluid, while its surfaces are spread out smooth- 
ly on the glass surfaces. In such preparations the vascular ar- 
rangement, the distribution of the nuclei of the neuroglia, and the 
ganglion cells and nerve fibers in their natural appearance and 
position, are brought to view with great distinctness. The 
processes of the pyramidal cells, which extend toward the periph- 
ery of the convolutions, may be followed up to three and four 
times the diameter of the field of vision of a one-fifth objective. 
The condition and position of the nuclei and nucleoli of the cells 
can be clearly pointed out, as also the roots at the base of the 
cells, and their origin. All this, however, will not visibly be al- 
tered when the fresh sections are soaked for staining in a carmine 
solution, to which a little glycerine has been added. They im- 
bibe a small amount only of the coloring material, yet some de- 
tails of structure may become thus more distinctly outlined. I 
have, therefore, most frequently in successive sections employe 
alternately both methods.” 
Fine Ruwines.—In speaking of the modern microscopic rulings 
on glass, which have been regarded with so great and deserved 
an interest by all physicists, one cannot be too careful to dis- 
criminate fully between those that are known to be ruled and 
those whose ruling has been attempted but not yet demon- _ 
monstrated. It is self-evident that in attempting to rule lines 
5,000,000 to the inch a band may be produced which does not 
consist of lines of that degree of fineness. There is no difficulty 
in arranging a machine to draw lines, theoretically, of any re- 
quired degree of.closeness. The register of a ruling engine can be 
So arranged and sub-divided as to indicate a spacing at the ruling 
point of one ten-millionth of an inch as easily almost as of one- 
tenth of an inch. But it may well be doubted whether such fine 
motion is actually imparted to the diamond point, or could be 
recorded upon the surface of the glass. It is becoming common 
to hear the higher bands of Mr. Fasoldt, claiming up to ten mil- 
lion lines to the inch, spoken of as actually ruled and only wait- 
ing an objective to reveal them. Such an error, made inadver- 
tently by persons who would avoid it by a little reflection, as 
made in the last number of one of the most popular microscopical 
journals, gives a lasting as well as erroneous impression to non- 
scientific persons. Mr. Fasoldt’s rulings are certainly remarkable 
and the lower bands are ruled with great SUCCESS ; but how ar 
up the scale they continue to be ruled as distinct lines is certainly 
at this time an undecided question. 
