OF THE BLOOD.
Physical characters of the blood: colour, fluidity,
specific gravity, temperature: quantity—Process
of coagulation—Constituents of the blood:
proportions—Constituents of the body contained in the
blood—Vital properties of the blood—Practical applications.
211. Supposing the human body to have been built up in the manner now
described, and to be in the full exercise of all its functions, the
integrity of its various structures is maintained, and their due action
excited by the blood. Out of this substance is formed the blandest
fluid, as the milk, and the firmest solid, as the compact bone. The
heart, capable of untiring action, as long as the blood is in contact
with its internal surface, becomes immovable soon after the supply of
this fluid is withdrawn; and in less than one minute from the time
it ceases to flow in due quantity and of proper quality through the
vessels of the brain, the eye is no longer capable of seeing, nor the
ear of hearing, nor the brain of carrying on any intellectual operation.
212. At the moment, and for some time after it has issued from its
vessel, the appearance of the blood is that of a thick, viscid, and
tenacious fluid; yet it is essentially a solid, composed of several
substances, each possessing its own distinct and peculiar properties,
the relation and combination of which cannot be considered without
exciting the feeling that our admiration of the structure of the animal
frame ought not to be confined to the mechanism of its solid parts, but
that the whole is admirable, from the common material of which it is
composed, to its most delicate and elaborate instrument.
213. The colour of redness is universally associated with the idea of
blood; but redness of colour is not essential to blood. There are many
animals with true, yet without red, blood; and there is no animal in
which the blood is red in all the parts of its body. The blood of the
insect is transparent; that of the reptile is of a yellowish colour;
that of the fish, in the greater part of its body, is colourless. Even
the red blood of the human body is not equally red in every part of it,
there being two distinct systems of blood-vessels, distinguished from
each other by carrying blood of different colours.
214. In the state of health, the specific gravity of human blood, water
being 1000, is 1080; from which standard it is capable of varying from
1120, the maximum, to 1026, the minimum.
215. The natural temperature of the human blood is 98°. From this it
is capable of varying from 104°, the maximum, to 86°, the minimum;
these changes being always the effect of disease.
216. It is estimated that the fluids circulating in the adult
man amount to about fifty pounds; of these it is calculated that
twenty-eight consist of red blood.
217. Fluid and homogeneous as the blood appears while flowing in its
vessel, when a mass of it is collected and allowed to stand at rest, it
soon undergoes a very remarkable change. First, a thin film is formed
upon its surface; this is followed by the conversion of the whole mass
into a soft jelly: this jelly separates into two portions, a fluid and
a solid portion. The solid portion again separates into two parts, into
a substance of a yellowish-white colour, occupying the upper surface,
and into a red mass always found at the under surface.
218. The process by which the constituents of the blood are thus
spontaneously disunited, and afforded in a separate form, is
denominated COAGULATION; the fluid portion separated by the process is
termed the SERUM; the solid portion the COAGULUM or CLOT; the white
substance forming the upper part of the clot, the FIBRIN; and the red
mass forming the under part of it, the RED PARTICLES.
219. Probably the process of coagulation commences the moment the
blood leaves its living vessel. In three minutes and a half it is
visible to the eye; in seven minutes the mass is formed into a jelly;
in from ten to twelve minutes the serum separates from the clot; in
about twenty the clot is divided into fibrin and red particles, when
the coagulation is complete; but occasionally the clot continues to
grow firmer and firmer for the space of twenty-four hours.
220. As soon as the coagulation commences, and during all the time the
blood preserves its heat, an aqueous vapour arises from it, termed
the HALITUS. The halitus consists of water holding in solution a
small quantity of animal and saline matter, which communicate to it a
fœtid odour of a strong and peculiar nature, manifest on approaching
a slaughter-house, and still more manifest in the slaughter-house of
human beings, a field of battle.
221. During the process of coagulation, as in every other in which a
fluid is converted into a solid, caloric is evolved.
222. During the process of coagulation carbonic acid is also extricated.
223. The process of coagulation affords three distinct substances,
the chief constituents of the blood, namely, serum, fibrin, and red
particles.
224. The serum, the fluid portion of the blood, when obtained
perfectly pure, is of a light straw colour, tinged with green.
Its taste is saline, and its consistence adhesive. It is composed
principally of water holding in solution animal and saline matter.
The animal matter gives it its adhesive consistence, and the saline
its peculiar salt taste. The chief animal matter contained in it is
the proximate principle termed albumen, which may be separated from
the water that holds it in solution by the application of heat and
by certain chemical agents. Heat being applied, when the temperature
reaches 160°, fluid serum is converted into a white opaque solid
substance of firm consistence. This is found to be albumen, which may
be also separated from the watery portion by the application of spirits
of wine, acids, oxymuriate of mercury, and several other chemical
substances. The quantity of albumen contained in 1000 parts of serum
varies from about 78, the maximum, to 58, the minimum.
225. If the albumen yielded by the serum be subjected to pressure, or
be cut into small pieces, there flows from it a watery fluid which is
termed the serosity. In meat dressed for the table, the serum of the
blood contained in the blood-vessels is converted by the heat into
solid albumen, from which, when cut, the serosity flows in the form of
gravy.
226. Besides albumen, serum holds in solution both a fatty and an oily
matter, in the proportion of about one part of each to 1000 parts of
serum. The proportion of its saline substances is about ten in 1000
parts. According to M. le Canu, who has made the most recent chemical
analysis of serum, 1000 parts contain, of
Water 906·00
Albumen 78·00
Animal matter, soluble in water
and alcohol 1·69
Albumen combined with soda 2·10
Crystallizable fatty matter 1·20
Oily matter 1·00
Hydrochlorate of soda and
potash 6·00
Subcarbonate and phosphate of
soda, and sulphate of potash 2·10
Phosphate of lime, magnesia,
and iron, with subcarbonate
of lime and magnesia ·91
Loss 1·00
227. All the animal and saline matter held in solution in the serum
being removed, the fluid that remains is water, the proportion of which
in 1000 parts varies from 853, the maximum, to 779, the minimum.
228. The second constituent of the blood, the fibrin, is the most
essential portion of it, being invariably present, whatever other
constituent be absent. While circulating in the living vessel,
fibrin is fluid and transparent; by the process of coagulation, it
is converted into a solid and opaque substance of a yellowish white
colour, consisting of stringy fibres, disposed in striæ, which
occasionally form a complete net-work (fig. CXI.). These fibres are
exceedingly elastic. In their general aspect and their chemical
relations they bear a close resemblance to pure muscular fibre, that
is, to muscular fibre deprived of its enveloping membrane and of its
colouring matter, and they form the basis of muscle. According to M.
le Canu, the proportion of the fibrin varies from seven parts in 1000,
the maximum, to one part in 1000, the minimum, the medium of twenty
experiments being four parts in 1000.
[Illustration: Fig. CXI.
A portion of the fibrin of the blood, showing its fibrous structure and
the striated or net-like arrangement of its fibres.]
229. The third constituent of the blood, the matter upon which its red
colour depends, though, as has been stated, entirely absent in certain
classes of animals, and in all animals in some parts of their body,
seems to be essential, at least to the organic organs, whenever they
perform their functions with a high degree of perfection. Thus in the
lowest class of vertebrated animals, the fish, while the principal part
of its body receives only a colourless fluid, its organic organs, as
the heart, the gills, the liver, are provided with red blood.
230. The red matter, wherever present, is invariably heavier than
the fibrin, and consequently, during the process of coagulation, it
gradually subsides to the lower surface, and is always found forming
the bottom of the clot. Its proportion to the other constituents varies
very remarkably, the maximum being 148, the minimum 68, and the medium
108, in 1000 parts of blood.
231. All observers are agreed that the red matter of the blood consists
of minute particles, having a peculiar and definite structure; but in
regard to the nature of that structure, there is considerable diversity
of opinion, which is not wonderful, since the particles in question
are so minute that they can be distinguished only by the microscope,
and since, of all microscopical objects, they are perhaps the most
difficult to examine, because, being soft and yielding, their figure
is apt to change, and because there is reason to suppose that their
substance is not uniform in its refractive power.
232. The earlier observers describe the red particles as being of
a globular figure, and accordingly name them globules. They conceive
that each globule consists of a central solid particle, enveloped in a
transparent vesicle. Recently, Sir Everard Home and Mr. Bauer in this
country, and MM. Prevost and Dumas on the continent, have revived this
opinion, and describe the red particle as consisting of a central solid
white corpuscle contained in an external envelop of a red colour. When
the blood is observed with the microscope in a living animal, flowing
in its vessels, only two substances can be distinguished, namely,
a transparent fluid and the red corpuscles. MM. Prevost and Dumas
contend that these two substances are the only component parts of the
blood. When the blood coagulates, they conceive that the red envelop
separates from the central white corpuscle; that these white corpuscles
unite together; that the aggregates resulting from this combination
are disposed in the form of filaments, which filaments constitute the
fibrin, while the red matter at the bottom of the clot is nothing but
the disintegrated envelops of the central particle. But this view is
not the common one. In general, physiologists conceive the fibrin to
be one constituent and the red particles to be another constituent of
the blood. Mr. Lister, who has successfully laboured to improve the
microscope, and who, together with his friend Dr. Hodgkin, have very
carefully examined with their improved instrument the red particles,
contend that the figure of these bodies is not globular, although
they state that the instant the particles are removed from the living
blood-vessels many things are capable of making them assume a globular
appearance; such, for example, as the application of water. With a
rapidity which, in spite of every precaution, the eye in vain attempts
to follow, the particles change their real figure for a globular form
on the application of the smallest quantity of pure water; while,
if the water contain a solution of saline matter, little alteration
is occasioned in the figure of the particles. According to these
observers, the red particles are flattened cakes, having rounded and
very slightly thickened margins (fig. CXII. 1). The thickness of the
margin gives to both surfaces the appearance of a slight depression
in the middle (fig. CXII. 1), so that the particles bear a close
resemblance to a penny piece. There is no appearance of an external
envelop. The circular and flattened cake is transparent; when seen
singly it is nearly if not quite colourless (fig. CXII. 1); it assumes
a reddish tinge only when aggregated in considerable masses.
[Illustration: Fig. CXII.
1. A particle of the human blood as it appears when transparent and
floating; 2. the same dry, seen as opaque, illuminated by a leiberkuhn;
3. the same as it appears when half the leiberkuhn is darkened; 4. a
particle of the frog's blood floating; 5. the same seen on its edge.
All the above objects are magnified 500 diameters[5].]
233. The red particle of the human blood is circular (fig. CXII. 1, 2,
3). It is circular also in all animals belonging to the class mammalia;
but in the three lower classes of vertebrated animals, the bird, the
reptile, and the fish, it is elliptical (fig. CXII. 4, 5).
234. The magnitude of the red particle of the human blood is variously
estimated from the two-thousandth to the six-thousandth part of an inch
in diameter. Bauer estimates it at the two-thousandth, Hodgkin and
Lister at the three-thousandth, Kater at the four-thousandth, Wollaston
at the five-thousandth, and Young at the six-thousandth part of an
inch. Its magnitude is uniformly the same in all individuals of the
same species, but differs exceedingly in the different classes. The
elliptical particles are larger than the circular, but proportionally
thinner; larger in fishes than in any other class of animals, and
largest of all in the skate.
235. When perfect and entire, the red particles indicate a disposition
to arrange themselves in a definite mode. They combine spontaneously
into columns of variable length (fig. CXIII.). In order to observe this
tendency, a small quantity of blood, the moment it is taken from its
living vessel, should be placed between two strips of glass or covered
with a bit of talc and placed under the microscope. When thus arranged,
a considerable agitation at first takes place among the particles.
As soon as this motion subsides, the particles apply themselves to
each other by their broad surfaces, and thus form piles or columns of
Considerable length (fig. CXIII.). The columns often again combine one
among another, the end of one being attached to the side of another,
sometimes producing very curious ramifications (fig. CXIII.). In
like manner, the elliptical particles apply themselves to each other
by their broad surfaces, but they are not so exactly matched as the
circular, one particle partially overlapping another, so that they form
less regular columns than the circular.
[Illustration: Fig. CXIII.
Columnar arrangement which the particles of the human blood assume
immediately after it is drawn from its vessel.]
236. The red particles, as far as is known, constitute a distinct and
peculiar form of animal matter: the red colour, according to some,
depending on an impregnation of iron; according to others, on an animal
substance of a gelatinous nature.
237. The exact proportion of the different substances contained in the
blood, according to the most recent analysis of it, that by M. le Canu,
is as follows, namely,
Water 786·500
Albumen 69·415
Fibrin 3·565
Colouring matter 119·626
Crystallizable fatty matter 4·300
Oily matter 2·270
Extractive matter, soluble in
alcohol and water 1·920
Albumen combined with soda 2·010
Chloruret of sodium and potassium,
alkaline phosphate,
sulphate, and subcarbonates 7·304
Subcarbonate of lime and magnesia,
phosphates of lime,
magnesia and iron, peroxide
of iron 1·414
Loss 2·586
--------
1000·
238. From the results of this analysis it is manifest that all the
proximate principles of which the different tissues are composed exist
in the blood, namely, albumen, the proximate principle forming the
basis of membrane; fibrin, the proximate principle forming the basis
of muscle; fatty matter, forming the basis of nerve and brain; and
various saline and mineral substances, forming a large part of bone,
and entering more or less into the composition of every fluid and solid.
239. The blood, which contains all the proximate constituents of the
body, and which, by distributing them to the various tissues and
organs, maintains their integrity and life, is itself alive. The
vitality of the blood is proved,—
240. i. By its undergoing the process of death, which it does just as
much as the heart or the brain, every time it is removed from the body.
While flowing in its living vessel, the blood is permanently fluid.
Its fluidity depends on a force of mutual repulsion exerted by its
particles on each other. That repulsive force is a vital endowment,
probably derived from the organic nerves so abundantly distributed
to the inner coat of the blood-vessels. When this vital influence
is withdrawn, which happens on the removal of the blood from its
vessel, the mass is no longer capable of remaining fluid; the fibrin
is converted into a solid; the red particles, instead of repelling,
attract each other, forming the crude aggregate at the bottom of
the clot; coagulation is thus a process of death; its commencement
indicates a diminution of the vital energy of the blood; during its
progress that energy is constantly growing less and less; the blood is
dying; and when complete, the blood is dead.
241. Hence in every state of the system in which the vital energy of
the blood is preternaturally increased, coagulation is proportionably
slow; in every state in which its energy is diminished, coagulation
is rapid. By copious and repeated blood-letting, the vital energy
is rapidly exhausted. The effect of blood-letting on coagulation
is determined by experiments instituted for the express purpose of
ascertaining it. Blood was received from a horse at four periods, about
a minute and a half intervening between the filling of each cup.
Minutes. Seconds.
In cup No. 1. coagulation began in 11 10
" 2. " " " 10 5
" 3. " " " 9 55
" 4. " " " 3 10
242. In like manner three cups were filled with the blood of a sheep,
at the interval of half a minute.
Minutes. Seconds.
In cup No. 1. coagulation began in 2 10
" 2. " " " 1 45
" 3. " " " 0 55
The same result was obtained in blood taken from a human subject. A
pound and a half of blood was removed from the arm of a woman labouring
under fever, a portion of which, received into a tea-cup on the first
effusion, remained fluid for the space of seven minutes; a similar
quantity, taken immediately before tying up the arm, was coagulated
in three minutes thirty seconds. These experiments demonstrate that
coagulation is rapid or slow as the vital energy of the blood is
exhausted or unexhausted, or that in proportion to the degree of life
possessed by the blood is the space of time it takes in dying.
243. This result is referable to the principle already shown to be
characteristic of living substance,—namely, the power of resisting,
within a certain range, the ordinary influence of physical agents.
The operation of this power is illustrated in a beautiful manner in
a series of experiments performed by Mr. Hunter on the egg and on
blood. This physiologist exposed a live, that is, a fresh egg to the
temperature of the 17th and the 15th degrees of Fahrenheit; it took
half an hour to freeze it. The egg was then thawed and exposed to 10°
less cold, namely, to the 25th degree of Fahrenheit; it was now frozen
in a quarter of an hour. A living egg and one that had been killed by
having been first frozen and then thawed, were put together into a
freezing mixture at 15°: the dead was frozen twenty-five minutes sooner
than the living egg. The undiminished vitality of the fresh egg enabled
it to resist the low temperature for the space of twenty-five minutes;
the vitality of the frozen egg having been destroyed, it yielded at
once to the influence of the physical agent. On subjecting blood to
analogous experiments, the result was found to be the same. Blood
immediately taken from the living vessel, and blood previously frozen
and then thawed, being exposed to a freezing mixture, a much shorter
period and a much less degree of cold were required to freeze the
latter than the former.
244. ii. The vitality of the blood is proved by the change it
undergoes in becoming a constituent part of an organized tissue.
The blood conveys to the several tissues the constituents of which
they are composed; each tissue selects from the mass of blood its
own constituents and converts them into its own substance, in which
conversion, since the blood always goes to the tissue in a fluid
form, the blood must necessarily pass from a fluid into a solid. In
the vessels the vital endowment of the blood maintains it permanently
fluid; in the structures the same power makes it and keeps it
solid. One and the same substance in one and the same body, in one
part is always fluid, in another always solid; the fluid is every
moment passing into the solid and the solid into the fluid, without
intermixture and without interference. Nothing analogous to this is
ever witnessed in inorganic matter, in physical mechanism; it is
peculiar to the organized body and distinctive of the mechanism of
life. Sometimes in physical mechanism we can perceive the mechanical
arrangements and distinctly trace them from beginning to end: in vital
mechanism, even when we can discern the mechanical arrangements, we can
seldom trace them beyond a step or two, and never from beginning to
end; but arrangement and adaptation we know there must be in that which
goes beyond, no less than in that which keeps within, our perception,
and we ought scarcely to question the existence of adjustments, because
they elude our sense, when probably the very reason why they do so is
that their delicacy and perfection immeasurably exceed any with which
sense has made us acquainted.
245. iii. The vitality of the blood is proved by the process of
organization. We can trace only a few steps of this process, but these
are sufficient to establish the point in question. Blood effused from
living vessels into the substance, or upon the surface of living
organs, solidifies without losing vitality. If a clot of blood be
examined some time after it has thus become solid, it is found to
abound with blood-vessels. Some of these vessels are obviously derived
from the surrounding living parts. The minute vessels of these parts,
as can be distinctly traced, elongate and shoot into the clot. The
clot thus acquires blood-vessels of its own. By degrees a complete
circulation is established within it. The blood-vessels of the clot act
upon the blood they receive just as the vessels of any other part act
upon their blood, that is transform it into the animal matter it is
their office to elaborate. In this manner a clot of blood is converted
into a component part of the body, and acquires the power of exercising
its own peculiar and appropriate functions in the economy.
246. But while, in this process, some of the vessels of the clot can
be distinctly traced from the surrounding living parts, others appear
to have no communication with those parts, at all events no such
communication can be traced. These vessels, the origin of which cannot
be found external to the clot, are supposed by some physiologists to
be formed within it. Within the living egg, during incubation, certain
motions or actions are observed spontaneously to arise, which terminate
in the development of the chick. Analogous motions arising within the
clot terminate, it is conceived, in the development of blood-vessels.
According to this view, a simultaneous action takes place in the clot,
and in the living part with which it is in contact; each shooting out
vessels which elongate, approximate, unite, and thus establish a direct
vital communication. Whether this view of the process of organization
be the correct one or not does not affect the present argument. It
is certain that a clot of blood surrounded by living parts becomes
organized; it is certain that no dead substance surrounded by living
parts becomes organized; it follows that the blood possesses life.
247. Health and life depend on the quantity, quality, and distribution
of the blood. The chief source from which the blood itself is derived
is the chyle: hence too much or too little food, or too great or too
little activity of the organs that digest it, may render the quantity
of the blood preternaturally abundant or deficient; or though there be
neither excess nor deficiency in the quantity of nourishment formed,
parts of the blood which ought to be removed may be retained, or
parts which ought to be retained may be removed, and hence the actual
quantity in the system may be superabundant or insufficient.
248. The relative proportion of every constituent of the blood
is capable of varying; and of course in the degree in which the
healthy proportion is deranged, the quality of the mass must undergo
a corresponding deterioration. The watery portion is sometimes so
deficient, that the mass is obviously thickened; while at other times
the fluid preponderates so much over the solid constituents, that the
blood is thin and watery. The albumen, the quantity of which varies
considerably even in health, in disease is sometimes twice as great,
and at other times is less than half its natural proportion. In some
cases the fibrin preponderates so much, that the coagulum formed by
the blood is exceedingly coherent, firm and dense; in other cases the
quantity of fibrin is so small, that the coagulation is imperfect,
forming only a soft, loose and tender coagulum, and in extreme cases
the blood remains wholly fluid. When the vital energy of the system
is great, the red particles abound; when it is depressed, they are
deficient. In the former state, they are of a bright red colour; in
the latter, dusky, purple, or even black. When the depression of
the vital energy is extreme, the power of mutual repulsion exerted
by the particles would seem to be so far destroyed as to admit of
their adhering to each other partially in certain organs; while in
other cases they seem to be actually disorganised, and to have their
structures so broken up, that they escape from the current of the
circulation as if dissolved in the serum, through the minute vessels
intended only for the exhalation of the watery part of the blood.
This fearful change is conceived to have an intimate connexion with
a diminution of the proportion of the saline constituents. Out of
the body, as has been shown, the red particles change their figure
instantaneously, and are rapidly dissolved when in contact with
pure water; while they undergo little change of form if the water
hold saline matter in solution. It would seem that one use of the
saline constituents of the blood is to preserve entire the figure and
constitution of the red particles. It is certain that any change in the
proportion of the saline constituents produces a most powerful effect
on the condition of the red particles. It is no less certain that
changes do take place in the proportion of the saline constituents.
In the state of health, the taste of the blood is distinctly salt,
depending chiefly on the quantity of muriate of soda contained in
it. In certain violent and malignant diseases, such, for example, as
the malignant forms of fever, and more especially that form of it
termed pestilential cholera, this salt taste is scarcely, if at all,
perceptible; and it is ascertained that, in such cases, the proportion
of saline matter is sensibly diminished.
249. The quality of the blood may be also essentially changed
by the disturbance of the balance of certain organic functions:
digestion, absorption, circulation, respiration, are indispensable
to the formation of the blood and to the nourishment of the tissues.
Absorption, nutrition, secretion, circulation, render the blood impure,
either by directly communicating to it hurtful ingredients, or by
allowing noxious matters to accumulate in it, or by destroying the
relative proportion of its constituents. Organs are specially provided,
the main function of which is to separate and remove from the blood
these injurious substances. Organs of this class are called depurating,
and the process they carry on is denominated that of depuration. The
lungs, the liver, the kidneys, are depurating organs, and one result at
least of the functions they perform is the purification or depuration
of the blood. If the lung fail to eliminate carbon, the liver bile,
the kidney urine, carbon, bile, urine, or at least the constituents
of which these substances are composed, must accumulate in the blood,
contaminate it, and render it incapable of duly nourishing and
stimulating the organs.
250. But though the blood be good in quality and just in quantity,
health and life must still depend upon its proper distribution. It
may be sent out to the system too rapidly or too slowly. It may be
distributed to different portions of the system unequally; too much may
be sent to one organ, and too little to another: consequently, while
the latter languishes, the former may be oppressed, overwhelmed or
stimulated to violent and destructive action. In either case health is
disturbed and life endangered.
251. Of the mode and degree in which food, air, moisture, temperature,
repletion, abstinence, exercise, indolence, influence the quantity,
quality, and distribution of the blood; of the mode in which the
condition of the blood modifies the actions both of the organic and
the animal organs; of the reason why health and disease are wholly
dependent on those states and actions, a clear and just conception
may be formed when the several functions have been described, and the
precise office of each is understood.