2i8 PHOTO-MICROGRAPHY [CH. VIII 



Thus among the very first of the experiments in photography the micro- 

 scope was called into requisition. And naturally plants and motionless objects 

 were photographed in the beginnings of the art when the time of exposure 

 required was very great. 



At the present time photography is used to an almost inconceivable degree 

 in all the arts and sciences and in pure art. Even astronomy finds it of the 

 greatest assistance. 



It has also accomplished marvels in the production of colored plates for 

 book illustrations, especially in natural history. For an example see Corn- 

 stock's Insect Life", 2d edition. 



Although first in the field, Photo-Micrography has been least successful of 

 the branches of photography. This is due to several causes. In the first 

 place, microscopic objectives have been naturally constructed to give the 

 clearest image to the eye, that is the visual image as it is sometimes called, is 

 for microscopic observation, of prime importance. The actinic or photo- 

 graphic image, on the other hand, is of prime importance for photography. 

 For the majority of microscopic objects transmitted light (\ 73) must be used, 

 not reflected light as in ordinary vision. Finally, from the shortness of focus 

 and the smallness of the lenses, the proper illumination of the object is 

 accomplished with some difficulty, and the fact of the lack of sharpness over 

 the whole field with any but the lower powers, have combined to make photo- 

 micrography less successful than ordinary macro-photography. So tireless, 

 however, have been the efforts of those who believed in the ultimate success 

 of photo-micrography, that now the ordinary achromatic objectives with 

 ortho-chromatic or isochromatic plates and a color screen or petroleum light 

 give good results, while the apochromatic objectives with projection oculars 

 give excellent results, even in hands not especially skilled. The problem of 

 illumination has also been solved by the construction of achromatic and 

 apochromatic condensers and by the electric and other powerful lights now 

 available. There still remains the difficulty of transmitted light and of so pre- 

 paring the object that structural details stand out with sufficient clearness to 

 make a picture which approaches in definiteness the drawing of a skilled 

 artist. 



The writer would advise all who wish to undertake photo-micrography 

 seriously, to study samples of the best work that has been produced. Among 

 those who showed the possibilities of photo-micrographs was Col. Woodward 

 of the U. S. Army Medical Museum. The photo-micrographs made by him 

 and exhibited at the Centennial Celebration at Philadelphia in 1876, serve 

 still as models, and no one could do better than to study them and try to equal 

 them in clearness and general excellence. According to the writer's observa- 

 tion no photo-micrographs of histologic objects have ever exceeded those 



for the purpose of book illustration [Donne & Foucault, 1845], the photo- 

 graphic use of collodion [Archer & Diamond, 1851], and finally, wholly 

 indebted for the origin of the gelatino-bromide process, greatest achievement 

 of them all [Dr. R. L,. Maddox, 1871]. See further for the history of Photo- 

 micrography, Neuhauss, also Bousfield. 



