32 Micro- spectroscopic Test for Blood-Stains. By Dr. Richardson. 



After thus examining the spectrum of the substance, you may 

 generally, by rotating the stage, cause the coloured fluid to partly 

 drain away from the solid portion, wherein, under favourable 

 circumstances, should the specimen be blood, the granular white 

 blood-globules become plainly visible, as do also cell- walls of the red 

 disks. Among the latter, if your mental and physical vision is keen 

 enough, you can by the aid of a 0^5 th immersion lens and an eye- 

 piece micrometer measure a series of corpuscles accurately enough 

 to discriminate human blood from that of an ox, pig, horse, or sheep. 



Lastly, to make assurance triply sure, lift up the thin glass 

 cover, wipe off the tiny drop of blood solution and clot you have 

 been examining on the folded edge of a thin piece of moistened 

 blotting-paper, let fall upon it a little fresh tincture of guaiacum, 

 and then a dro]) of ozonized ether, which will at once strike the 

 deep blue colour of the guaiacum test for blood. 



In this way I have actually obtained these three kinds of 

 evidence, to wit, that of spectrum analysis, that of the microscope, 

 and that of chemical reaction, from one single particle of blood, 

 which, judged by a definite standard,* certainly weighed less than 

 one fifteen-thousandth, and probably less than one twenty-five- 

 thousandth, of a grain. 



Although Mr. Sorby claims to be able to demonstrate the 

 absorption bands from a single red blood-corpuscle, yet, as his 

 instructions for detecting hlood- stains, quoted above from the 

 ' Quarterly Journal of Science,' vol. ii. p. lUS, are reiterated in his 

 paper in the 'Monthly Microscopical Joiu-nal' of July 1871, p. 9, 

 and seem to be those solely relied upon by Dr. Herepath, in the 

 ' Chemical News,' 1868, vol. i. p. 124, by Prof. L. S. Beale, in his 

 'How to Work with the Microscope,' London, 1868, p. 222, by 

 Dr. W. B. Carpenter, in 'The Microscope and its Eevelations,' 

 5th ed., London, 1875, p. 121, and by Prof. A. S. Taylor, in Guy's 

 Hospital Pieports, 18i)9, p. 274, and in his 'Principles and Practice 

 of Medical Jurisprudence,' 1873, vol. i. p. 542, and since W. Preyer t 

 advises no more delicate mode than making and examining a 

 solution in a watch-glass, I feel justified in ofl'ering my method to 

 microscopists and medical jurists, as an improvement in the ordinaiy 

 and facile ajipUcation of spectrum analysis to blood-stains, by which 

 this important test is rendered at least one hundred times as delicate 

 as it has hitherto been when employed according to the directions 

 of the highest British or Continental authorities, thus enabling us 

 to detect a recent blood-spot on white muslin covering one ten- 

 thousandth of a square inch and forming a speck scarcely visible to 

 the unassisted eye. — Bead before the Biological and Microscopical 

 Section of the Academy of Natural Sciences, Philadelphia, U.S.A. 



* See ' Handbook of Medical Microscopy,' Phila., 1871, p. 283. 

 t 'Die Blutkrystalle,' Jena, 1871, s. 114. 



