2i2 THE MICROSCOPE. 



many eminent microscopists in making such a statement, knowing 

 full well that my reasons and proofs will be demanded and tested 

 ere I am credited. Let me give an outline of the methods employed 

 in reaching such a bold conclusion, leaving the details of the experi- 

 ments to be described hereafter. 



If the blood stain offered for identification is deposited upon 

 the polished surface of steel, iron, glass or wood, and the problem 

 to be solved reduced to the single question — is this human or dog's 

 blood ? — excluding the blood of all other mammals,* the labor of the 

 investigation is greatly simplified. If, however, as is usually the 

 case with such examinations, the blood stains are presented upon 

 fabrics of wool or cotton, the process becomes more tedious, but the 

 results are scarcely less accurate or exact, provided the stain offers a 

 sufficient number of corpuscles to complete the necessary experi- 

 ments and are unmixed with chemicals or other extraneous matter 

 likely to distort or destroy them. 



Our experiments include a large number of methods and re- 

 agents for restoring dried corpuscles. Perhaps, the plan that affords 

 as good results as any is the one as substantially recommended by 

 Dr. Richardson, of Philadelphia. 



If the stain for examination is deposited upon any of the smooth 

 and hard surfaces first mentioned, a drop of a solution of bichloride 

 of mercuryf [% of one per cent, solution] is deposited in the centre 

 of the spot and stirred and scraped gently, with a cataract needle, 

 the dried speck being broken up as finely as possible by means of 

 the keen edge of the needle. Immediately this mixture is trans- 

 ferred to a half-inch cover-glass, first having breathed upon the 

 glass, while it is held by forceps, and the breathed-upon-surface ap- 

 plied to the mixture. A sufficient quantity will adhere to the glass; 

 but, should it fail in so doing, remove the drop to the cover-glass by 

 means of a clean camel's hair brush. Invert the cover-glass to 

 which the fluid adheres upon a slide. Then, apply a solution of 

 eosine [five grs. to the ounce of distilled water] to the edge of the 

 cover-glass. Touch the opposite edge of the glass with a piece of 

 blotting paper, when, as the mercurial solution is removed, the 

 staining fluid takes its place. Permit it to remain two minutes, 



* It is presumed to be an admitted fact that the blood corpuscles of the horse, cow, pig, 

 sheep and goat, being so much smaller than man's, their identification is easy of procurement. 

 t Dr. Richardson uses >£ of one per cent, of common salt solution. 



