MICROSCOPIC DAGUERREOTYPES. 
mandibles terminated by two teeth, the form of the entire organ 
being that of a pincers. The skin, which is of a tongh leathery 
texture, is elegantly marked by sinuous and parallel tracings, 
bearing some resemblance to engine-turning. Wrinkles are in 
some places seen upon it, as if it were divided into separate 
segments, united edge to edge,- like the bones composing the 
human skull; upon the legs, the skin is finely granulated and 
not striated, as upon the body ; several long hairs issuing from the 
legs are seen in the figure. 
68. Although the general fidelity of microscopic drawings made 
with a camera may be relied upon, yet, as has been already 
observed, the more minute details are executed by the artist in 
the same manner as that in which a portrait-painter produces his 
effects, and in whatever degree the artistic skill of the draughts¬ 
man may be manifested in such parts of the drawing, the rigorous 
fidelity demanded by science, even in the minutest arts, cannot be 
claimed for them. 
69. Under these circumstances, other means, ensuring more 
rigorous accuracy, and rendering the drawing independent 
altogether of those impulses which imagination and taste never fail 
to impart to the pencil even of the most conscientious artist, have 
been eagerly sought by naturalists, and have been happily sup¬ 
plied by photography. The magnified image of the object under 
examination, produced by a solar microscope, is received upon a 
prepared daguerreotype-plate, or a leaf of photographic paper, and 
there the optical image delineates itself with the most unerring 
fidelity and rigorous accuracy. 
70. This felicitous application of the photographic art, to the 
promotion of natural science, after some experimental essays, 
more or less successful, was first carried out, so as to be available 
for the practical purposes of science, by Dr. Donne, assisted by 
M. Leon Foucault, in 1845. In that year Dr. Donne published 
an atlfe to illustrate his course on microscopic anatomy and. 
physiology, which had appeared in the previous year, consisting 
of twenty plates, on each of which were four microscopic engrav¬ 
ings, made from daguerreotype plates which had been produced 
in the manner above described. I avail myself gladly of the 
kind permission of the authors of this work, and of Mr. 
Bailliere, its publisher, to reproduce four of these engravings upon 
the scale on which they are given by the authors. 
71. The blood of animals is not, as it seems at first view to be, 
a homogeneous liquid holding in complete solution certain, sub¬ 
stances, and destitute of all solid and concrete matter ; if it were 
so, we could not follow its course through the vessels in which it 
moves, as we do so easily and distinctly with the microscope. 
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