The proportion between the cruor and se- 
rum of the blood varies much in diflerent ani- 
mals, and even in the same animal in different 
circumstances. '1 he most common propor- 
tion is about one part of cruor to three parts 
of serum ; but in many cases the ciuor ex- 
ceeds or falls short of this quantity ; the limits 
of the ratios of these substances to each other 
appear, from a com parison of the conclusions 
ot most of those who have written accurately 
on the subject, to be l 1 and 1 4 ; but tire 
first case must be very rare indeed. 
The cause of this spontaneous decomposi- 
tion of blood has not hitherto been ascertain- 
ed. The coagulation takes, place equally in 
close vessels and in the open air, whether the 
blood is allowed to cool, or is kept at the 
temperature at which it is when it issues fro nr 
the animal ; neither is the coagulation pre- 
vented by diluting it with water. 
1. The serum is of a light greenish- yellow 
colour ; it lias the taste, smell, and feel, ot the 
blood, but its consistence is not so great. 
Its mean specific gravity is about 1.0287. It 
converts svrup ot violets to a green, and 
therefore contains an alkali. On examination, 
Houelle found that it owes this property to a 
portion of soda. When heated to the tem- 
perature of 156% the serum coagulates, as 
iiarvey first discovered. It coagulates also 
when boiling water is mixed with it; but if 
serum is mixed with six parts of cold water, 
it does not coagulate by heat. \Y hen thus 
coagulated, it has a greyish-white colour, and 
is not unlike the boiled white of an egg. If 
the coagulum is cut into small pieces, a 
muddy fluid may be squeezed from it, which 
has been termed the serosity. After the se- 
paration of this fluid, if the residuum is care- 
fully washed in boiling water and examined, it 
will be found to possess all the properties of 
coagulated albumen The serum, therefore, 
contains a considerable proportion ot albu- 
men. Hence its coagulation by heat, and 
the other phenomena which albumen usually 
exhibits. 
If serum is diluted with six times its weight 
of water, and then boiled to coagulate the 
albumen, the liquid which remains after the 
separation of the coagulum, if it is gently 
evaporated till it becomes concentrated, and 
then is allowed to cool, assumes the form of a 
jelly, as was first observed by De Haem 
Consequently it contains gelatine. 
If the coagulated serum is heated in a silver 
vessel, the .Surface of the silver becomes black, 
being Converted into a sulphured Hence it 
is evident that it contains sulphur ; and j 
Proust has ascertained that it is combined 
with ammonia in the state of a hydrosul- 
phuret. .... i r 
If serum is mixed with twice its weight ot 
water, and after coagulation by heat, the al- j 
bumen is separated by filtration, and the 
liquid slowly evaporated till it is considerably 
concentrated, a number ot crystals are depo- 
sited when the liquid is left standing in a 
cool place. These crystals, first examined 
by Rouclle, consist of carbonat ot soda, mu- 
riat of soda, besides phosphat of soda and 
phospliat of lime. The soda exists in the 
blood in a caustic state, and seems to be com- 
bined with the gelatine and albumen. The 
carbonic acid combines with it during evapo- 
ration. 
Thus it appeals that the serum of the blood 
contains albumen, gelatine, hydrosulphuret 
SERUM. 
of ammonia, soda, rnuriat of soda, phosphat 
of soda, and phosphat of lime, These com- 
ponent parts account for the coagulation oc- 
casioned in the serum by acids and alcohol, 
and the precipitation produced by tan, acetat 
of lead, and other metallic salts. 
With respect to the other part, the cruor, 
or clot, as it is sometimes called, is of a red 
colour, and possesses considerable consist- 
ence. Its mean specific gravity is about 
1.245. If this cruor is washed carefully by 
letting a small jet of water fall upon it till 
the water runs off colourless, it is partly dis- 
solved, and partly remains upon the searce. 
Thus it is separated into two portions, viz. 
(1.) A white, solid, elastic substance, which 
has all the properties of fibrina. 2. The por- 
tion held in solution by the water, which 
consists of the colouring matter, not however 
in a state of purity, for it is impossible to se- 
parate the cruor completely from the serum. 
We are indebted to Bucquet for the first 
precise set of experiments on this last watery 
solution. It is of a red colour. Bucquet 
proved that it contained albumen and iron. 
Menghini had ascertained, that it blood is 
evaporated to dryness by a gentle heat, a 
quantity of iron may be separated from it by 
the magnet. The quantity which he obtained 
was considerable; according to him, the blood 
of a healthy man contains above two ounces 
of it. Now, as neither the serum nor the 
fibrina extracted from the cruor contains iron, 
it follows of course, that the water holding 
the colouring matter in solution must contain 
the whole of that metal. 
This watery solution gives a green colour 
to syrup of "violets. When exposed to the 
air, it gradually deposits flakes, which have 
the properties of albumen. When heated, a 
brown-coloured scum gathers on its surface. 
If it is evaporated to dryness, and then mixed 
with alcohol, a portion is dissolved ; and the 
alcoholic solution yields by evaporation a re- 
siduum, which lathers like soap in water, and 
tinges vegetable blues green; the acids occa- 
sion a precipitate from its solution. This 
substance is a compound of albumen and soda. 
Thus we see that the watery solution contains 
albumen, iron, and soda. 
Fourcroy and Vauquelin have ascertained 
that the iron is combined with phosphoric 
acid, and in the state of subphosphat of iron ; 
thus confirming an opinion which had been 
maintained by Sage, and announced as a fact 
by Gren. If the residuum obtained by eva- 
porating the watery solution of the colouring 
matter of blood to dryness is burnt in a cru- 
cible, there will remain a deep-red ferrugi- 
nous substance, amounting to 0.045 of the 
blood employed. Nitric acid digested on 
this residuum dissolves a portion, which is 
phosphat of iron, and is precipitated white by 
ammonia, but assumes a red colour when 
treated with pure potass. When lime-water 
is poured into the potass employed, phosphat 
of lime precipitates. By this- treatment they 
ascertained, that-iA of the residuum consist- 
ed of subphosphat of iron. Now phospliat 
of iron is soluble in acids, but insoluble in 
water; when treated with pure alkalies, it 
loses a portion of its acid, assumes a red 
colour, and is converted into subphosphat. 
Hence it is evidently the soda of the blood 
which reduces it to that state, or at least 
maintains it in that state. Subphosphat of 
4 N 2 
iron readily dissolves in albumen and in 
serum. 
When new-drawn blood is stirred bristly 
round with a stick, or the hand, the whole of 
the fibrina collects together upon the stick) 
and in this manner may be separated altoge- 
ther from the rest of the blood. The l ed 
globules, in this case, remain behind in the 
serum. It is in this manner that the blood is 
prepared for the different purposes to which 
it is put ; as clarifying sugar, making pud- 
dings, &c. After the fibrina is thus separatee!, 
the blood no longer coagulates when allowed 
to remain at rest, but a spongy flaky matter 
separates from it, and swims on the surface. 
When blood is dried by a gentle heat, wa- 
ter exhales from it, retaining a very small 
quantity of animal matter. in solution, and 
consequently having the odour of blood'. 
Blood dried in this manner being introduced 
into a retort and distilled, there comes over 
first a clear watery liquor, then carbonic acid 
gas, and carbonat of ammonia, which crys- 
tallizes in the neck of the retort ; after these 
products there come over a fluid oil, carbo- 
nated hydrogen gas, and an oily substance 
of the consistence of butter. The watery 
liquor possesses the property of precipitating 
from sulphat of iron a green powder : muri- 
atic acid dissolves part of this powder, and- 
there remains behind a little Prussian blue. 
Consequently this watery liquor contains both 
an alkali and prussic acid. 
9216 grains of dried blood being put into a 
large crucible, and gradually heated, at first 
became nearly fluid, and swelled up consi- 
derably, emitted a great many fetid fumes ot 
a yellowish colour, and at last took lire anch- 
burned with a white flame, evidently owing 
to the presence of oil. After the flame and 
the fumes had disappeared, a light smoke 
was emitted, which affected the eyes and the 
nose ; it had the odour of prussic acid, and 
reddened moist paper stained witty vegetable 
blue. At the end of six hours, when the mat- 
ter had lost five-sixths of its substance, it 
melted anew, exhibited a purple flame on its 
surface, and emitted a thick smoke. This 
smoke affected the eyes and nostrils, and 
reddened blue paper, but it had not the smell 
of prussic acid. When a quantity of it was 
collected and examined, it was found to pos- 
sess the properties of phosphoric acid. The 
residuum amounted to 181 grains; it had a 
deep-black colour, and a metallic brilliancy ; 
and its particles were attracted by the mag- 
net. It contained no uneombined soda, 
though the blood itself, before combustion, 
contains it abundantly; but water extracted 
from it rnuriat of soda ; part of the remainder 
was dissolved by muriatic acid, and of course 
was lime ; there was besides a little silica, 
which had evidently been separated from the 
crucible. The iron had been reduced during 
the combustion. 
Such are the properties of blood, as far as 
they have been hitherto ascertained by expe- 
riment. We have seen that it contains the 
following ingredients : 
1. Water, 
2. Fibrina, 
3. Albumen,. 
4. Gelatine, 
5. Hydrosulph. of ammonia, 
6. Soda, 
7. Subphosphat of iron, 
