The purpose of the present chapter, so far as our knowledge extends,
is to describe the chemical history of those bodies which are
characterized as being rather organized than organic; as constituting
not merely a product of the vital operations of the being, but the
mechanism itself by which these vital operations are carried on;
as making part of the tissues essential to its proper organization
and life; and as being, while in connection with the animal and
participating in its life, protected from the truly chemical
reactions of their proper elements, which after the death of the
animal, especially when in contact with air or water, rapidly assume
simpler forms of union, and breaking up the complex animal tissue
into a crowd of binary compounds, under the change well known as
putrefaction.
In connection with these substances which form the basis of the
organs and tissues of the animal frame, will be brought under survey
the processes by which, from the atmosphere or from the materials
of our food, the substance of our organs is continually renewed,
their growth provided for, and the conditions necessary for the
continuance of life and health maintained. The following elucidation
of the materials which enter into the composition of the human body
is of extreme importance, as it will help to demonstrate why the
chemicals employed in the former processes of embalming have been
selected in preference to others.
_Of Fibrine._—This substance constitutes the basis of the muscular
tissue, and forms an important constituent of the blood. In the
latter it exists dissolved during life, but separates after death or
extraction from the body, producing, with the coloring material, the
phenomenon of coagulation. In the muscles the fibrine is arranged in
a truly organized and living condition, constituting the contractile
fibres, in which it is so interwoven with nervous and vascular
filaments as to render its isolation impossible. To obtain pure
fibrine, therefore, we have recourse to blood, which, if immediately
on being drawn it be briskly agitated with a little bundle of twigs,
does not coagulate, but the fibrine is deposited on the twigs in
soft, tenacious masses, which, being washed to remove any adhering
coloring matter, and digested in alcohol and ether to remove any
traces of fatty substances which may adhere to it, constitute pure
fibrine; which may be dried by a gentle heat, and appears then as
a yellowish, opaque mass, hard, tasteless and inodorous. If it be
at all transparent, this results from traces of adhering fat. It is
insoluble in water, alcohol and ether; it absorbs, however, so much
water as to treble its weight, and thereby recovers the volume,
softness and flexibility it possessed before being dried.
If sulphate of soda or nitrate of potash be added to newly drawn
blood, its coagulation is prevented; and if fibrine be digested in a
strong solution of nitre, it dissolves, forming a thick liquid, which
is coagulated by heat, by alcohol, by acids, and is precipitated by
the _salts of mercury_, _lead_ and _copper_, and by yellow prussiate
of potash. This property of fibrine will again come under our notice.
_Of Albumen._—This substance is even more extensively distributed
through the animal frame than fibrine. Like fibrine, it exists in two
conditions, one soluble and one insoluble in water; but whereas the
fibrine becomes insoluble almost instantly on being withdrawn from
the body, albumen may retain that state for an indefinite time, and
its history is therefore more complete. In its soluble form it exists
in the blood, in the serous secretions, in the humours of the eye; in
the soluble or coagulated form it constitutes a portion of most of
the solid tissues.
_Soluble Albumen._—This is obtained in the solid form by evaporating
to dryness, at a temperature which does not exceed 120°, the serum
of blood; the dry mass is yellow, transparent, hard, tough, and
contains, besides the albumen, the salts and some other constituents
of the blood in minute quantities; these are extracted by digestion
in alcohol and ether, which leave the albumen pure. When thus
completely dry it maybe heated beyond 212° without passing into the
coagulated condition; if digested in cold water it gradually swells
up and finally dissolves. This solution, when heated to a temperature
between 140° and 150°, coagulates; if dilute, the solution may even
be heated to 165° without coagulating, and when present in very small
quantity the albumen may not separate until the water boils.
When once coagulated in this manner, albumen is totally insoluble
in water; it is then changed into its second form. The solution
of albumen is precipitated by _alcohol_, by _acids_ and _metallic
salts_, exactly as the solution of fibrine in saltpetre; the only
distinction that can be drawn between the two is that the saline
solution of fibrine is partially decomposed by the addition of a
large quantity of water.
The precipitates yielded by a solution of albumen with metallic
salts are mixture of two distinct substances, one a compound of
albumen with the acid, the other a compound of albumen with the
metallic oxide; the former is generally somewhat soluble, the latter
insoluble, and hence results the application of albumen as an
antidote to mineral poisons, as corrosive sublimate and blue stone.
Albumen is also coagulated by many organic bodies, as tannic acid
and creosote, which acts catalytically, as a very minute quantity
of it coagulates a large quantity of albumen, without entering into
combination with it.
_Of the Gelatinous Constituents of the Tissues._—When the skin,
cellular or serous, tissues, tendons, and some forms of cartilage,
as that of bones, are boiled in water, they dissolve in great part
and form a solution which gelatinizes on cooling. Some of these
tissues, as the skin, dissolve easily and almost completely; others
dissolve but partly, and leave behind a quantity of coagulated
albumen. In most kinds of cartilage a very prolonged boiling is
necessary to extract a sensible quantity of gelatine. These various
tissues are thus found to consist of albumen and gelatine, united
in various proportions, and each presenting various degrees of
condensation of texture; but by boiling they may be completely
separated from each other.
Gelatine is insoluble in alcohol and ether. When a solution of
gelatine is long exposed to the air, it undergoes a commencement of
putrefaction, and loses its property of gelatinizing.
The action of reagents on gelatine is in some cases of high interest,
it is not precipitated by solutions of either ordinary or basic alum,
but if a solution of common salt be also mixed, the gelatine falls
down, combined with alumina, as it decomposes the muriate of ammonia
which is then formed. On this principle is founded the manufacture of
white leather, by a kind of tanning with alum.
The most important compound of gelatine is that with tannic acid,
which constitutes ordinary leather; this reaction is so distinct that
one part of gelatine in five thousand of water is at once detected by
the infusion of galls.
Many chemists consider that gelatine is merely a product of the
decomposition of albumen and fibrine by boiling water, and not a true
constituent of the tissues; but this idea is thought to be incorrect,
on the following grounds: First, pure fibrine or albumen gives no
gelatine by boiling; second, in the process of tanning, the tannic
acid combines with gelatine in a skin which has never been boiled;
and third, that we can easily understand why some tissues give more
gelatine than others by the different degrees of condensation of
their structure. But it is rather considered that gelatine bears the
same relation to the tissues of the skin or cellular membrane that
protein does to the fibrine of the blood, being really a product of
its death and decomposition, _though the only representative of it
which we can have_.
_Of the Fatty Constituents of the Tissues._—The fatty bodies,
although contributing essentially to the support of the animal frame,
are mere secretions, and do not form any portion of its organized
tissues. The substances properly included under the present head are
the constituents of the nervous tissue, such as it is found in the
brain, the spinal cord and the nerves.
In the composition of the brain, it is easy to distinguish three,
perhaps five, distinct substances of a fatty nature; the most
characteristic and important is called cerebrote; in composition it
resembles albumen, containing a large quantity of nitrogen.
_Saline, and Extractive Constituents of the Tissues._—We find in all
the animal tissues small quantities of a great variety of salts,
the same as those which will be hereafter noticed as existing in the
blood, to the presence of which in the substance of the tissues they
are probably due. In the tissue of the bones and teeth, however,
these saline matters are deposited in much greater quantities, and in
disease and old age bony deposits occur in all those tissues, which
yield true gelatine on boiling. The composition of the bones will be
hereafter noticed.
_Of the Composition of the Tissues and of the Secretions in Health
and Disease._—Having described thus individually the constituents
of the tissues, we shall now present such results as have been
hitherto obtained as to the quantitative composition of the organized
tissues formed by their reunion, their secretory products and morbid
alterations.
The skin of animals is a congeries of finely constructed organs,
sensitive and secretory, imbedded in a peculiar tissue, which is one
of those most yielding gelatine, whence the process of tanning skins.
On the surface of the skin there is secreted a substance, which,
though varying in anatomical structure and appearance exceedingly,
as it forms the fine epidermis, the nails, the hair, etc., is yet
throughout all their shapes identical in chemical character, and
may be described as the same substance. The principal mass of hair
is composed of the same substance as horn, but the color is due to
an oil which may be extracted by ether. If by virtue of the sulphur
contained in hair a solution of litharge in some limestone water
blackens it, a solution of nitrate of silver will also blacken the
hair, but by a deposition of the metal.
The perspiration from the skin varies in nature according to the
part of the body; it is generally acid, contains traces of albumen,
fatty matter and the salts of the blood; it often contains, also,
an odoriferous, volatile principle, characteristic of the animal by
which it is secreted.
_Cellular and Serous Tissues._—These tissues are constituted of
gelatinous materials similar to that in the skin, and hence dissolve
by boiling water, being converted into gelatine. In the natural
condition of these membranes their surface is moistened by a watery
liquid, which, accumulating in excessive quantity, gives rise to the
dropsies of the cavities, or of the cellular tissues. This serum
of the cavities is clear and colorless. The cells of the cellular
tissues, in which fat is usually deposited, are often filled up by an
albuminous material having considerable analogy with casein; it is
thus that the diffused hardening of the cellular tissue and the local
white tumors have their origin.
_Of the Muscular Tissue._—From what has been already said of fibrine,
it is evidently the essential element of the muscular tissues, and
forms with water almost the whole of their parts.
_Of the Bones._—In vertebrated animals with osseous skeletons the
earthy material, in all cases, consists principally of phosphate of
lime, with phosphate of magnesia, carbonate of lime and soda. By
digesting a bone in dilute muriatic acid, all of these inorganic
salts are removed, and the cartilage remains, preserving perfectly
the form of the bone.
The teeth present, in their combinations, the greatest analogy to
bone; the principal and organized substance of the teeth is indeed
true bone, containing indeed less cartilage and more phosphate of
lime than other bones. The enamel, which is an inorganic secretion
from the surface of the long tooth, is almost destitute of any animal
matter.
_Of the Composition of the Blood._—Blood is, in the higher classes
of animals, an opaque, thick, red fluid; it has a salty and nauseous
taste, and a peculiar smell, resembling that of the animal whence it
has been derived.
When the blood of any red blooded animal is allowed to rest, it
gradually forms a soft jelly, from which, after some time, a thin
yellowish fluid (serum) separates, while the red jelly or coagulum
contracts in volume and acquires great consistence. If this
coagulation of the blood takes place slowly, the upper portion of
the coagulum becomes white or pale yellow; forming thus, the buffy
coat. There is no doubt that the blood, while in connection with the
animal, participates in its life, and the phenomena of coagulation
are to be referred to a new arrangement of its materials consequent
on the loss of that vitality.
The serum of the blood, when coagulation has been perfect, is of a
yellowish, sometimes greenish, color; its taste is dull and salty;
it is thick fluid, like olive oil; when heated to 140° it coagulates.
If we examine under the microscope the appearance presented by blood,
we find that it consists of a great number of red particles swimming
in a nearly colorless liquor. These red particles are flattened
disks; in man they are round. Their size is variable, being in man
from one four-thousandth to one eight-thousandth of an inch in
diameter, but larger in other animals.
The blood contains a large quantity of _albumen_, partly dissolved
and remaining in the serum after coagulation, partly in a solid
state, forming the great mass of the globules.
In the living body the blood also contains fibrine in solution, but
this separates soon after extraction from the body; it assumes a
solid form, and investing, as a sponge, the red globules, forms with
them the coagulum.
The fibrine is thus the element active in the coagulation of the
blood, the globules being but passively engaged in it. In addition
to this essential organic element, the blood contains a variety of
salts, as common salt, phosphate of magnesia, ammonia and lime,
lactates of soda and magnesia. The best analyses of the blood are
those of Lecanu, and the results for blood and serum are that they
contain, in the human subject of each sex:
Water, 75.00
Albumen, 5.00
Globules, 7.14
Fibrine, .20
The fatty substance of the blood is a mixture of cholesterine
with stearic and oleic acid and a peculiar fatty substance termed
seroline, the history of which is yet incomplete. None of the fats of
the brain, however, seem to exist in the blood.
The chemical history of fibrine and albumen having been already
given, it remains only to describe the peculiar coloring matter,
for the most accurate knowledge we possess concerning which, we are
indebted to Lecanu’s elaborate researches on the blood.
Pure hematosine or coloring matter, when it is coagulated, is a
dark brown mass, tasteless and inodorous; when heated it does not
smell, but swells up and evolves ammoniacal products; it is insoluble
in water, alcohol and ether; _it forms, with the mineral acids,
compounds which are insoluble in water but soluble in alcohol_.
By caustic alkalies it is dissolved with a red-blood color, and
these combinations are soluble in water, alcohol and ether.
Hematosine contains neither phosphorus nor sulphur, but iron in large
quantities. The state in which iron exists in hematosine has been,
up to the present day, an object of much discussion among chemists;
but with the knowledge we now possess of hematosine in its pure form,
we must consider the iron to be an integral part of its organic
constitution, as sulphur in albumen, or arsenic in alkarsine, and
the opinion of its being oxydized and combined with the true organic
element as a kind of salt can no longer be supported. If a solution
of hematosine be acted on by chlorine gas, a white, flocculent
precipitate is produced, and the solution contains chloride of iron.
Although hematosine is the coloring principle of the globules of the
blood, it is present but in very small quantity; one hundred parts
of dried globules containing but four to five parts of hematosine;
in the blood globule the hematosine exists in its uncoagulated
state, and possesses properties somewhat different from those of its
coagulated form.
A solution of the colored blood globules in water, when exposed
to the air, becomes of a brighter red color, being thus partially
arterialized; it is _coagulated also by alcohol and by acids_; the
hematosine then passes into the condition of insolubility, already
described.
The colorless ingredient in the blood globules has already been
spoken of as being albumen, with which, indeed it is identical
in properties, but differ in some points. It has been termed
globuline. In its uncoagulated condition it can not be separated from
hematosine, and is there distinguishable from albumen, principally
by being insoluble in even a very dilute saline solution, which
dissolves albumen readily. It is, hence, that the globules of the
blood swim unaltered in the serum, but are readily dissolved by pure
water.
If the blood, when extracted from the vein, is received into a vessel
containing a solution of glauber’s salt, coagulation is prevented,
as the fibrine remains dissolved, and by filtering the liquor so
obtained, the serum and water pass off and the globules remain,
mixed only with little of the salt. The globuline cannot, however, be
separated from hematosine, except by acids, which, as described in
the preparation of hematosine, then combine with the globuline.
_Alteration of the Blood in disease._—The examination of the state
of the blood in disease, although presenting important relations
to pathology and to practice, has been conducted in a manner too
disconnected and superficial to produce any satisfactory results.
This branch of chemical pathology has, however, been taken up by the
illustrious Andral and Gavaret, who have published the result of the
analysis of the blood in three hundred and sixty cases of disease.
Their researches have enabled them to recognize four classes of
diseases, in which the composition of the blood is essentially
altered, though in different ways.
The first class presents as a constant alteration, an increase in
the quantity of fibrine; it includes diseases remarkably different
in their locality and form, but all belonging to the class of acute
inflammations in some cases of morbid deposition, as in tubercle and
cancer, a similar increase in the quantity of fibrine is found, but
it may be doubted whether it be due to abnormal growth or to the
inflammatory action which accompanies it.
In the second class the fibrine remains stationary, or even
diminishes in quantity, while the globules increase in proportion to
the fibrine. The diseases which belong to this class, are, continued
fevers without local inflammation, and some form of cerebral
hemorrhages.
_Cerebral Hemorrhages._—In the third class, the fibrine remaining
unchanged, there is a remarkable diminution in the quantity of
globules; of these diseases, chlorosis may be taken as an example,
and in the fourth class it is no longer the fibrine or the globules
which are the subject of the morbid change, but the quantity of the
albumen in the serum is diminished; of this class of affections is
Bright’s disease.
It has been observed, that in cholera the blood becomes so thick as
to arrest the circulation, and contains from thirty to forty-five per
cent. of solid matter; it is then, also, less strongly alkaline than
healthy blood; this is connected probably with the matters vomited
and evacuated, which are strongly alkaline, and contain a quantity of
albumen.
The blood has been found, occasionally, in cases of Diabetes
Mellitus, to contain traces of sugar. The great discordance of the
results obtained, may result, perhaps, from the sugar contained in
the blood only for a short time after meals, and then being rapidly
evacuated by the kidneys. In the jaundice the green coloring matter
of the bile has been found mixed with the blood.
Other observations of morbid constituents of the blood are too
indefinite to justify me in occupying space with them.
_Color of the Blood._—In the living body, the blood in the veins and
arteries is well known to differ essentially in color; in the former
being of a dark purple-red, in the latter of a bright vermilion
color. The change from the venal to the arterial state occurs during
the passage of the blood through the capillary vessels of the
lungs, where it is exposed to the action of an extensive surface of
atmospheric air; while the arterial blood, in traveling the general
capillary system of the body, assumes the red, dark condition in
which it is carried back to the heart by the veins. Yet, although the
vital properties of the blood depend essentially upon this change
of color, we are not able to connect it with any alteration in the
composition of the constituents of the blood, or even in their
relative proportions.
Arterial and venous blood contains sensibly the same quantity of
water, fibrine, globules, albumen and salts; and, by analysis, the
composition of those bodies is found to be identical, no matter what
kind of blood they may be derived from. To trace the difference of
nature between arterial and venous blood, it is therefore necessary
to study it under different points of view than its approximate or
elementary composition. So far as we have yet explained it, the air
which has been employed in respiration, is found to have undergone
an important change of constitution; its volume is but slightly,
if at all, altered; but a quantity of oxygen has disappeared, and
is replaced by carbonic acid, in generally equal volume. Air
which has been once respired is found to contain from three to
four per cent. of carbonic acid, and if the same quantity of air
be continually breathed, the animal dies with all the symptoms of
narcotic poisoning. When the carbonic acid has accumulated to from
eight to ten per cent., the action of the air in expiration is
therefore to remove carbon from the blood. The quantity so taken
from the system in twenty-four hours is very large, and makes up the
principal portion of that element which we take in with our food;
yet, such is the activity with which its assimilation provides, that
no perceptible change in the solid elements of the blood can be
perceived.
It was, at one time, a much disputed point, whether the carbon so
separated from the system was directly excreted from the lungs, and
carried off as it were, by contact with the oxygen of the air, or
whether the oxygen was first absorbed by the blood and carried by
the circulation to every portion of the body, where it combined with
the carbon, which was there present in excess, and the carbonic acid
so produced, being dissolved by the venous blood, was thrown off on
arriving at the surface of the atmosphere, in the lungs. The progress
of science has, however, finally decreed in favor of the latter view,
to which the fullest confirmation has been given by the careful and
elaborate researches of Magnus.
_Gases in the Blood._—It was found that both arterial and venous
blood contain dissolved quantities of gases, oxygen, nitrogen and
carbonic acid, which amount to from one-tenth to one-twentieth the
volume of the blood; the proportions of these two gases to each other
are different in arterial and venous blood; the oxygen in arterial
blood being about one-half of the carbonic acid, while in the venous
blood it seldom amounts to more than one-fifth; the difference is
greatest in young persons, and probably is proportional to their
activity of nutrition.
The quantity of nitrogen appears to be the same in both kinds of
blood, making from one-fifth to one-tenth of the gaseous mixture.
The physico-chemical conditions of respiration are simply explicable
upon these results, by the principle of gaseous diffusion, the fine
lining pulmonary membrane being permeable to gases. When the venous
blood arrives at the surface of the lungs, a portion of the carbonic
acid which it contains is evolved, and a quantity of oxygen gas
absorbed in place of it; these two quantities are not necessarily
equal at each moment, though ultimately they become so, and hence
the volume of oxygen absorbed is generally, though not universally,
equal to that of the carbonic acid given out. There appears, from the
presence of nitrogen in equal quantity in both kinds of blood, to be
an absorption and evolution of that gas, simply from physical laws,
and independent of any application of it to the nutrition of the
animal; hence the volume of nitrogen in air is sometimes increased,
and at others diminished, by respiration, and a man evolves much
nitrogen when respiring an atmosphere of oxygen and hydrogen,
while it has been shown that the rate of nutrition of a man is
proportionate to the quantity of nitrogen it receives as food, and
that none of that principle is really assimilated from the air.
It is still by no means easy to decide upon the changes of color
which occur in the blood during respiration; for this should appear
connected, not merely with the presence of certain gases in the
blood, but upon a true change in the composition of hematosine, which
analysis cannot direct.
Stevens first attracted the attention upon the influence which saline
bodies have upon the color of the blood. If dark, venous blood is put
in contact with a solution of common salt, glauber salt, nitre, or
carbonate of soda, it becomes as vermilion colored as if it had been
truly arterialized; on the contrary, the presence of carbonic acid
impedes this action, and gives to blood, so reddened by a salt, not
in excess, the dark tint of venous blood.
If we consider, therefore, the arterial tint to be due to the
material combination of the coloring matter with the saline
constituents of the serum, this will be darkened, when, by passing
through the capillary system, the blood takes up an excess of
carbonic acid; and again, in the lungs, when the carbonic acid is
replaced by oxygen, the vermilion color is restored, not by any
active agency of the oxygen, but by the natural tint of saline
hematosine becoming evident.
Although this theory of the change of color is by no means free from
objection, it still appears to be better founded than any other that
has been proposed.
_Animal Heat._—The phenomena of respiration consisting mainly in
the conversion of carbon into carbonic acid by union with oxygen,
the heat which is developed in the body of all red blooded animals
has been naturally referred to that source; and as we know that
the change from the arterial to the venous condition of the blood
occurs at every point of the system, the almost complete equality
of temperature throughout the body in health is explained. That
the great source of heat is the respiratory process, is abundantly
proved by the temperature being highest in those animals, and in the
same animal, at those periods when the circulation is most rapid
and the quantity of air consumed the greatest. But it has been
calculated that the heat evolved by the combustion of the quantity
of carbon thrown off from the body in twenty-four hours is no more
than eight-tenths of the quantity generated in the body during that
time, and the origin of the remainder must be found in the action of
the muscles and the nervous power, which appears of itself to be a
distinct source of animal heat.