§ 40*] EXAMINATION OF BLOOD. 65 
The wave lengths corresponding to the numbers on the scale in the 
diagram are as follows :— 
W.L. 
W.L. 
732 
4 
510-2 
656 
5 
480-0 
589-2 
6 
458 
549-8 
7 
438 
IX.—Examination of Blood, or of Blood-Stains. 
§ 40. Spots, supposed to be blood—whether on linen, walls, or 
weapons—should, in any important case, be photographed before any 
chemical or microscopical examination is undertaken. Blood-spots, 
according to the nature of the material to which they are adherent, 
have certain naked-eye peculiarities— e.g., blood on fabrics, if dry, has 
at first a clear carmine-red colour, and part of it soaks into the tissue. 
If, however, the tissue has been worn some time, or was originally 
soiled, either from perspiration, grease, or filth, the colour may not be 
obvious or very distinguishable from other stains ; nevertheless, the 
stains always impart a certain stiffness, as from starch, to the tissue. 
If the blood has fallen on such substances as wood or metal, the spot is 
black, has a bright, glistening surface, and, if observed with a lens, 
exhibits radiating fissures and a sort of pattern, which, according to 
some, is peculiar to each species ; so that a skilled observer might 
identify occasionally, from the pattern alone, the animal whence the 
blood was derived. The blood is dry and brittle, and can often be 
detached, or a splinter of it, as it were, obtained. The edges of the 
splinter, if submitted to transmitted light, are observed to be red. 
Blood upon iron is frequently very intimately adherent; this is specially 
the case if the stain is upon rusty iron, for hsematin forms a compound 
with iron oxide. Blood may also have to be recovered from water in 
which soiled articles have been washed, or from walls, or from the soil, 
etc. In such cases the spot is scraped off from walls, plaster, or masonry, 
with as little of the foreign matters as may be. It is also possible to 
obtain the colouring-matter of blood from its solution in water, and 
present it for further examination in a concentrated form, by the use of 
certain precipitating agents. 
In the following scheme for the examination of blood-stains, it is 
presumed that only a few spots of blood, or, in any case, a small quantity, 
are at the analyst’s disposal. 
1. The dried spot is submitted to the action of a cold saturated 
solution of borax. This medium (recommended by Dragendorff x ) 
does certainly dissolve out of linen and cloth blood-colouring matter 
1 “ Untersuchungen von Blutspuren,” in Maschka’s Handbuch, Bd. i. Half band 2. 
