172 The Microscope. 



PHOTO -MICROGRAPHY. 



W. M. GRAY. WASHINGTON, D. C. 



TT is the purpose of the present article to give the methods used, 

 -*- and the results obtained by the writer, in photo -micrography 

 of sections of animal tissues. The subjects used were sections of 

 tumors, pathological organs and normal histology. 



Sections intended for photo-micrography must be exceedingly 

 thin, and at the same time properly stained. To obtain the former 

 quality, a mechanical microtome is necessary, as the sections should 

 be evenly cut, and should range from ^uVo to the s^oVti ^^ ^^ i^*^^ 

 in thickness, the object being tg have as nearly as possible a single 

 layer of cells, and at the same time, still preserve the general out- 

 lines of the structure of the tissue. Of the imbedding methods for 

 obtaining the proper sections, paraffine used by the interstitial 

 process, is preferable, as it allows of such evenness and thinner in 

 cutting. Celloidin may be used in some cases, but does not give 

 such satisfactory results, for the reason, it is not always possible to 

 make as thin sections. 



In staining tissues for photo -micrography, two objects are 

 desired, intensity and differentiation. Of the innumerable staining 

 agents, those most suitable, and easiest applied, are carmine, haema- 

 toxylon, and a few of the aniline dyes. Of all the carmines, 

 borax carmine, if used correctly, invariably gives the most perfect 

 results. In using this dye, it is always better to overstain, and 

 and bleach with a strong acid solution; HCl. 10 per cent, in alcohol 

 70 per cent. ; the bleaching must be carried to the point where the 

 nuclei appear sharp and distinct, and yet the protoplasm be not 

 entirely discolored, this result may be easily gained by a little 

 practice. 



Hsematoxylon ranks second as a stain for photo-micrography. 

 It has the disadvantage of being nearly useless for the wet- plate 

 process, yet it will answer as well as carmine for certain dry-plate 

 methods. While the aniline dyes are more applicable to the stain- 

 ing of bacteria, yet good results may be obtained with sections, 

 especially by the use of Bismarck Brown; this is the ideal stain for 

 the we-tplate process, but unfortunately does not answer perfectly 

 for photographing with high magnifying powers; the reason for 

 this is, that while it is seemingly a perfect nuclear stain, yet the 

 protoplasm retains enough of the color to obscure the definition, or 

 more properly, is rendered nearly as non- actinic as the nucleus. 



