Micro-spedrosGojpic Test for Blood-Stains. By Dr. Richardson. 31 



weigh from one twenty-five-thousandth to one fifty-thousandth of a 

 grain). Then with a cataract-needle deposit on the centre of the 

 cover, near your blood-spot, a drop of glycerine about the size of this 

 period (.), and with a dry needle gently push the blood to the 

 brink of your microscopic pond, so that it may be just moistened 

 by the fluid. Finally, invert your slide upon the thin glass cover 

 in such a manner that the glycerined edges of the cavity in the 

 former may adhere to the margins of the latter, and, turning the 

 slide face upwards, transfer it to the stage of the microscope. 



By this method, it is obvious, we obtain an extremely minute 

 quantity of strong solution of haemoglobin, whose point of greatest 

 density (generally in the centre of the clot) is readily found under 

 a ^-inch objective, and tested by the adjustment of the spectroscopic 

 eye-piece. After a little practice it will be found quite possible 

 to modify the bands by the addition of sulphuret of sodium solution, 

 as advised by Preyer. 



In order to compare the delicacy of my plan with that of 

 Mr Sorby, a spot of blood one-tenth of an inch square may be 

 made on a piece of white maslin, the threads of which average one 

 hundred to the inch. When the stain is dry, ravel out one of the 

 coloured threads and cut off and test a fragment as long as the 

 diameter of the filament, which will of course be a particle of stained 

 fabric measuring one one-hundredth of the minimum-sized piece 

 directed by Mr. Sorby. When the drop of blood is old, a larger 

 amount of material becomes requisite, and you may be obliged to 

 moisten it with aqua ammoniee, or with solution of tartrate of 

 ammonium and protosulphate of iron ; but in the criminal case 

 referred to, jive months after the murder, I am able from a scrap of 

 stained muslin one-fiftieth of an inch square to obtain well-marked 

 absorption bands, easily discriminated from those produced by a 

 solution of alkanet-root with alum and those caused by infusion of 

 cochineal with the same salt. 



In cases of this kind, where the greatest possible economy or 

 even parsimony of material is needful, 1 would advise the following 

 mode of procedure for proving and corroborating your proof of the 

 existence of blood, so that its presence in a stain may be affirmed 

 with absolute certainty. 



From a suspected blood-spot upon metal, wood, leather, paper, 

 muslin, or cloth, scrape with a fine sharp knife two or three or 

 more minute particles of the reddish substance, causing them to 

 fall near the middle of a large thin glass cover. Apply in close 

 proximity to them a very small drop of three-fourths per cent, salt 

 solution,* bring the particles of supposed blood-clot to its edge, and 

 proceed as I have already directed. 



* See my paper " Oa the Value of High Powers in the Diagnosis of Blood- 

 Stains," 'American Journal of the Medical Sciences,' July, 1874, p. 109. 

 VOL. XV. D 



