158 
POPULAR SCIENCE NEWS. 
[October, 1890. 
intellect if micro-photographs of the two 
fluids were thrown upon a screen, while the 
most thorough and painstaking explanation 
of their varying shape and size would make 
but little impression. Thousandths of a mil- 
limetre are magnitudes which are almost 
incomprehensible to the average mind. 
Although with the recent improvements 
introduced into the process, no particular 
knowledge of chemistry is necessary to prac- 
tice the photographic art successfully, yet the 
physician, from his scientific education and 
his training in careful and ^elicate manipula- 
tion, is especially fitted to find pleasure and 
profit in it. A satisfactory and complete 
outfit may be obtained for about ten dollars, 
and from that upwards as high as one's 
inclination may lead or one's purse allow. 
And even if one finds but limited use for his 
camera in a professional line, it will certainly 
prove a most satisfactory investment as sup- 
plying a means of diversion from professional 
cares, of which no one stands more in need 
than the tired and often overworked physician. 
[Original in Popular Science New9.] 
THE MEDICO-LEGAL EXAMINATION OF 
BLOOD AND BLOOD-STAINS. 
The detection of blood and blood-stains for 
medico-legal and other purposes is a subject of great 
interest and importance to the physiological chem- 
ist and the general practitioner of medicine, for 
these are not infrequently called upon to state 
whether a given stain is one of blood or not, and to 
determine, as far as possible, — if it be found to be 
a blood-stain,— from what animal or creature the 
blood has been drawn. It may be well to mention, 
in the very outset of this discussion, that it is 
impossible to state positively that a given stain is 
one of human blood, or even that a given specimen 
of fluid blood has been drawn from man. 
If a quantity of fluid be brought for examination, 
— as is rarely the case, — it is easy to ascertain whether 
it is blood or not, by examining a portion under the 
microscope, when the corpuscles — if present — will 
identify the specimen as blood. Moreover, by 
means of the microscope we can determine whether 
the blood be that of a mammal or not, for the red 
blood-cells of all mammals have depressed centers 
and are non-nucleated, and all are circular discs, 
except in one tribe, viz. , the camel family (camelida) , 
in which the discs are oval instead of circular. In 
vertebrata lower than the mammalian scale there is 
a characteristic difference. Birds, reptiles, amphibia, 
fishes, etc., all — excepting that creature, lowest in 
the scale of fishes, whose blood is colorless, viz., 
the amphioxus — have red blood-corpuscles, but they 
. all have a distinct nucleus, and all are oval, except 
in a low order of fishes which have rounded, nucle- 
ated discs. 
Granted that we have demonstrated a given speci- 
men of blood to be mammalian, we are now unable 
to tell from exactly what mammal it has been taken, 
on account of the varying size of the red corpuscles, 
upon which we must depend. Thus, the average 
diameter of the human red blood-corpuscles is 7.7 
micro-millimetres, the largest measuring about 9 7 
m. mm. and the smallest only 4 S m. mm. in diam- 
eter. Now, in this range is included the average 
size of the red corpuscles of the blood of most 
domestic animals. The average diameter of the 
red blood-corpuscles of the dog is 7.3 m. mm. ; that 
of the rabbit is 6 9 m. mm. ; of the cat, 65m. mm. ; 
of the ox and pig, 60 m. mm. ; of the horse, 5.4 
m. mm. ; of the sheep, 50 m. mm. ; and of the goat, 
41 m. mm. Thus we see that the determination 
of the kind of blood depends upon the form, size, 
etc., of the red corpuscles, and that even with fluid 
blood there cannot be positive evidence that a given 
specimen is human blood. But in these examina- 
tions greater practical difhculties than those already 
mentioned are usually met with, for a dried stain is 
usually presented, and not fluid blood ; and, more- 
over, ofttimes the article containing the stain has 
been subjected to washing or to other processes 
of time and exposure ; and yet, with all these difll- 
culties, we may still be able to say that a stain is or 
is not blood. 
In the first place, let us suppose that an ordinary, 
quite recent, dried stain is submitted. In this case 
we can cause the red corpuscles — if it be a blood- 
stain — to absorb fluids and a surae their original 
form and average shape, and average diameter. 
But when they imbibe the fluids we have no means 
of causing them to imbibe precisely the same amount 
that they have lost in drying, and so assume exactly 
the same size as before ; but we can say positively 
whether the stain is one of mammalian blood or 
not, since even the red corpuscles in dried mamma- 
lian blood will, under the circumstances just de- 
scribed, again assume their rounded, or circular, 
form, and will never show a nucleus. 
The most delicate means at our command for 
determining whether a given stain is or is not 
blood; is the spectroscope. In virtue of the red 
coloring matter of the red corpuscles, — the hcemo- 
glohin, — the spectroscope will identify a blood-stain 
with accuracy, even when the stain is years old. 
Both reduced and oxy-h.emoglobin give character- 
istic absorption spectra. Ha;moglobin spectra, 
however, are the same whether the blood be 
obtained from a mammal or not. 
Let us now suppose that we have an old stain on 
an old garment, which we wish to examine to deter- 
mine whether it be a blood-stain or not. We scrape 
off" some of the fabric marked by the stain, — never 
using it all, — and prepare a watery solution of the 
coloring pigment, which, if the stain be blood, will 
give the characteristic absorption spectrum of hicmo- 
globin, or of one of its derivatives. The simple 
direct-vision spectroscope is well adapted to this 
work, and especially that form which is so arranged 
that two specimens may be studied at the same 
time. In order to obtain the characteristic spectra 
of ha;moglobin for study and for comparison with 
spectra which we are examining, a standard solution 
is made by dissolving one volume of blood in one 
hundred volumes of water, and this is viewed 
through a layer one centimetre thick. Any glass 
vessel with parallel sides of the proper width apart 
will answer for holding the solution. These vessels 
are sold by dealers under the name of ha;matinome- 
ters, and we also have the very convenient hemato- 
scope for the same purpose. The light employed 
may be either the natural light of the sun, or may 
be artificial ; in the former case with ordinary direct- 
vision spectroscope, a well-illuminated white wall 
usually furnishes very good illumination. 
Solutions of pure ha,'moglobin, as well as the red 
corpuscles themselves, or diluted mixtures of blood 
and water, in the aerated condition, exhibit the well- 
marked and peculiar spectrum of oxy-h;einogIobin. 
This spectrum is distinguished by the existence 
of two absorption bands between the lines (Fraun- 
hofer's) D and E, and situated the one in the yellow 
and the other at the commencement of the green. 
The first of these absorption bands is comparatively 
narrow, well defined, and dark, and is placed at 
about one-fifth the distance from D to E. The 
second is double the width of the first, but is less 
dark, and is not so well defined, and occupies nearly 
the last half of the space between D and E. 
Beyond the second band the light of the spectrum 
gradually diminishes, and ceases altogether about 
the termination of the blue, midway between F and 
G. As the strength of the solution is increased, 
the bands become broader and deeper, and both 
ends of the spectrum are absoibed ; and if now the 
strength of the solution be still further increased, 
the two bands above described unite to form one 
very broad band. 
If an aqueous solution of oxy-ha;moglobin be 
exposed to the air for some time — ordinary blood 
being such a solution — Its spectrum undergoes a 
change; the two oxy-ha;moglobin bands between D 
and E become faint, and a new band appears in the 
red near C. The solution, it will be observed, has 
lost its blood-red color, assumed a brownish tinge, 
presents an acid reaction, and is precipitable by 
basic lead acetate. This change is due to the 
decomposition of hajmoglobin and the production 
of methamoglobin, and since time, by the action 
of the air and sunlight, causes this change in blood, 
the spectrum just described is the one generally 
given by old stains. When in the analysis this 
spectrum is given we add a reducing agent, — usually 
ammonium sulphide, — when reduced h^'moglobin is 
produced, which gives its characteristic spectrum. 
Then, by shaking up this reduced hicmoglobin with 
air, we obtain oxy-ha;moglobin, which gives us its 
spectrum. 
The spectrum of reduced (or deoxidized) ha;mo- 
globin is entirely different from that of oxy-h;cmo- 
globin. Instead of the two bands between D and 
E, there is a single band, the darkest portion of 
which occupies the space which intervened between 
the two bands of dilute oxy-ha;moglohin. The 
entire band is not well defined, but usually covers 
about three-fourths of the distance from D to E, 
and is shifted further to the left than were the two 
bands of oxy-ha;moglobin. Solutions of oxy-htemo- 
globin may be reduced by means of the air-pump, 
bypassing hydrogen or nitrogen gas through them, 
and by reducing agents, of which Stoke's fluid is 
very convenient. This latter is a solution of ferrous 
tartrate. When the reduced hajmoglobin spectrum 
has been obtained, the solution is shaken up with 
air, and the oxy-ha;moglobin spectrum should be 
given upon further examination with the spectro- 
scope. 
By the action of heat, or of acids or alkalies in 
the presence of oxygen, haemoglobin is split up 
into a substance known as hamatin aftd a proteid 
residue. If no oxygen be present, instead of hiema- 
tin, hamochromogeh (reduced hiematin) is produced, 
which, however, speedily undergoes oxidation into 
hx'matin. Both hsmatin and reduced h;ematin 
give special spectra. So in analyzing a given 
specimen we should make hicmatin by adding to 
the solution of haemoglobin a small quantity of 
acetic acid, when the liquid will be observed to 
become brown in color, and spectrum analysis 
reveals a distinct absorption band in the red between 
C and D; this is the spectrum of ha-matin in acid 
solution. If we render the liquid alkaline by the 
addition of ammonia, a single absorption band is 
seen also between C and D, but differs from that 
of acid h;ematin in that this latter is placed very 
near to C, while in the alkaline ha;matin the band is 
very near the line D, and there is also to be noticed 
a marked shading of the blue end of the spectrum 
in addition. If, now, a reducing solution — as 
Stoke's reagent — be added to the liquid, the two 
absorption bands of reduced hivmatin are obtained, 
which resemble those of oxy-luemoglobin, but need 
not be mistaken for those of the latter, as they arc 
