MICROSCOPIC DAGUERREOTYPES. 



mandibles terminated by two teeth, the form of the entire organ 

 being that of a pincers. The skin, which is of a tough 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. Donn6, assisted by 

 M. Leon Foucault, in 1845. In that year Dr. Donn6 published 

 an atlas 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. 



H 2 99 



