Blood is the name given to the liquid enclosed in the arteries that beat, and in the veins corresponding to these arteries. See Artery and Vein.

Blood appears at first inspection homogeneous, red, and susceptible to coagulation in all parts of the body; but different experiments have taught us that it has different characteristics.

Hydrostatics has allowed us to discover that there is something volatile in blood , that is continually given off by blood in the form of a gas, and whose odor is between that of the bad smell of urine, and that of sweat. This gas, contained in its own vessels, appears aqueous, and as if charged with a color close to alkali.

The blood of the most healthy man coagulates in a trembling mass, easy to break apart: it thickens more as one exposes it to a heat less than that of boiling water, and even of 150 degrees. It has been observed to come together like jelly in the veins during life, and in those who were dying of violent fevers. The red part of blood constitutes the principal component of this coagulation, which has a red color, and communicates it to all the other parts of blood . This same component of blood , which can come together in an unformed mass when in repose, when exposed to a slight chill, to a heat of 150 degrees, and mixed with vinous spirits, with mineral acids, is however soft, unless it is hardened by a trituration such as it experiences in life, or by some similar jolts. It is heavy, and almost more than an eleventh the volume of a similar amount of water; it is very flammable when its phlegm is removed: the red portion constitutes half and more of the mass of blood in sanguinary temperaments, and the serous a third of the mass; during a fever it is reduced to a fourth or fifth part.

That which next presents itself, is the whitish and yellowish component of blood ; and although it appears homogeneous, it is not however so. It is in general thirty-eight percent heavier than an equal volume of water; and lighter by a twelfth than coagulum . It coagulates if exposed to a heat of 150 degrees, if mixed with acids and vinous spirits, and if agitated, its clots are harder than those of the red component of blood . They are so glutinous, that one cannot reduce them, in a membrane, and finally, in a substance as solid as antler. It is this humor that produces the tough substance that is seen in the blood of those suffering from pleurisy, polyps and artificial membranes. One finds in this serous, in addition to the albuminous component that may coagulate, a simple water that makes up the greatest portion, and something mucous-like that runs, and that nevertheless cannot be coagulated like the albuminous component, neither by fire nor by acids.

Only corruption and the force of air heated to 96 degrees may occasion a fetid dissolution of the whole mass of blood , and above all of serum ; for the serous portion is the most susceptible: less so the red portion. With time, the red component and the lymph finally change into a fetid and volatile exhalation, and leave a sediment in the bottom of the container in which they have been decomposed.

Once dissolved by decomposition, blood can no longer coagulate; and once it has been coagulated with vinous spirits, it can no longer dissolve.

Other than all these components that are easily discerned in blood , it also contains a great quantity of sea salt, distinguishable by its slightly salty taste, and at times with a microscope. Taste, as well as chemical analysis, demonstrate that it is also charged with earth, mixed with the most fluid components, and above all with oil. There is, finally, in blood a great quantity of non-elastic air, as is demonstrated by the corruption of blood and serum , and by pumping the air that surround it. It does not follow that the globules are air bubbles, for they are specifically heavier than serum .

Chemistry has provided us with different means of discovering the nature of blood . If we expose blood taken from a healthy man to a small flame, there evaporates out of it a great quantity of water that made up five sixths of all its mass; it is almost flavorless, and yet marked by a fetid oil that smells stronger and stronger as the distillation nears its end. Exposing the remains to a stronger flame produces alkaline liquids of various types, the first of which is fetid, bitter, red and made from a volatile salt dissolved in water, which makes up the twelfth part of the blood as a whole.

Before and during the separation of the oil there appears a dry, volatile salt that attaches to the side of the glass in branched flakes: it is small in quantity, and makes up at least a fiftieth part of blood .

The other liquid, which appears more slowly, is heavier, and yellowish at first, then black, then as sticky as pitch, bitter and inflammable; it is the oil of human blood , it is small in quantity, and makes up about the fiftieth part.

There remains at the bottom the charcoal of blood , very porous, inflammable, which detonates when one sets fire to it and is reduced to ashes. After washing, one recovers from this ash a salt mixed with sea salt and a stable alkaline, and a bit of earth; the stable salt makes up barely an eightieth part of blood , of which almost a fourth is alkaline. By means of a violent flame, one obtains something acidic from this alkali, similar to the spirit of blood , and having at the same time some resemblance to the elements obtained from vegetables, the character of which is not totally destroyed; as a result it is found in animals who live on vegetables, as well as in man. The earth, that constitutes about a one hundred and fiftieth part, is charged with some particles attracted by a magnet. Distilled serum gives the same principal components as blood as a whole; it furnishes however less oil and much more water.

This analysis demonstrates that some liquids in blood are heavier and more tenacious than others; that some are aqueous, inflammable, and that a great portion of blood is more susceptible to corruption and of an alkaline nature: for as long as blood is not altered, and is protected from corruption and too much heat, it does not alkalinize, nor become bitter, it is to the contrary sweet and a little salty; it is however bitter during certain illnesses, and very disposed to corruption. For example, scurvy, during which it eats at the vessels that enclose it; dropsy, when the water becomes almost alkaline. One finds in that of insects an alkaline chalk, which effervesces with acids.

Violent acids and vinous spirits coagulate blood . Sweet acids, alkaline salts, even when stable, and above all when volatile, vegetable acids and saltpeter, dissolve it; it does not effervesce with any salt. Violent movement, too much exterior heat, corrupt blood .

If one examines freshly drawn blood in a glass tube, or in the veins of living animals, through a microscope, one distinguishes red globules, soft, of variable appearance, and which constitute what one properly calls the cruor , or that part of blood enclosed in the arteries and the sanguinary veins.

These globules swim in a less dense fluid, in which one distinguishes with a microscope yellow globules, smaller than the red ones, which were formerly of this color; and which through heat and rubbing change into smaller similar ones. Great men, after many experiments, evaluated the diameter of a red globule of blood as one pouce [2.7 cm].

One observes, after the most careful examination with a microscope, in the pale water that remains and in which the first globules are swimming, globules as transparent as water, and some small specks of salt.

It is from these experiments, compared one to the other, that all our knowledge of blood is taken. We know thus that blood is composed of globules that unite in an unformed mass when the gas that holds them apart is evaporated, because their force of attraction is then increased. The red component of blood , when dried and set aflame, demonstrates the inflammable nature of these globules if one throws it in fire; which also proves the pyrophoric substance that one obtains from human blood , and it is very likely that the sticky oil that one obtains from blood by means of a violent flame also comes from this source.

The yellowish serum that also appears to be composed of globules swimming in water, is as we have described it above. It is found in a type of aqueous and finer liquamen , in which one cannot distinguish the water particles from the other principal components, in smaller quantities, of which it is composed; principal components that fire degenerates into alkaline salts. Distillations of saliva, of mucous, of the humor of light sweat, furnish more proofs.

One cannot exactly determine the quantity of blood ; it is known that the weight of the humors very much surpasses that of the solid components; but several of these humors do not circulate, such as fat and the glutinous sap that unites the different components. If we judge by heavy bleedings that have not cause the loss of life, by experiments conducted on animals, from which all the blood was taken, by the capacity of the veins and arteries, the circulating humors may be estimated to weigh at least 50 pounds, of which the fiftieth part constitutes that which we call true blood ; the arteries contain about the fifth part of it, and the veins the other four.

The proportion of these elements is not always as we have described it up until now: exercise, being in the prime of life, increase the blood enclosed in the sanguinary vessels, its redness, its force, its density, the cohesion of its components, the rigidity of the coagulated serum , its weight and its alkaline principles; to the contrary, if one is young, inactive, if one drinks only water, and lives on vegetables alone, all these causes diminish the volume of blood in the sanguinary vessels, making the aqueous components less abundant, and increasing the proportion of serum and mucous that it contains; old age increases the red portion, and diminishes the gelatinous portion.

The red component of blood appears above all to produce heat, because the heat is always in proportion to this component: it stops it in the vessels of the first order, because the size of its globules prevents it from passing through; and as they receive from the heart a movement in common with the other components, they have more speed than these do, because of their greater density; so, for this reason, they give movement to the liquids of the inferior orders; that is why, when the red component of blood is overly diminished by frequent bleedings, the blood remains in the smallest vessels; one becomes fat, hydropic, and thus the renewal of the mass of blood appears to depend on the presence of a suitable amount of this red component; in effect, bleeding make blood degenerate from its red and thick nature into a pale and serous humor.

Serum , principally that which coagulates, is especially destined to nourish the components, to dissolve nutrients, to water the external and internal surfaces of the cavities of the human body, to maintain the suppleness of the solids, the movement of the nerves, of vision, etc . M. Haller, Physiol .

The red globules of blood differ from those found in the chyle only in that they are composed of several; their color comes only from this combination, for when one separates them, they regain their whiteness; from which it follows that everything that appears red in blood exposed to the air is in the end converted to serosity; for the small globules that separate one from another regain their whiteness. The same thing happens to blood when it is enclosed in the body; for after rolling about some time in its vessels, its nature changes; its globules are constantly whipped by the vessels, which, helped by the heat that arises, divides the components of the blood, and reduces them in the end to a serosity, that is filtered by the channels of the viscera, or given off by the pores of the lungs and the skin.

The cause of this redness has given rise to many systems; the most generally accepted is the mixture of the saltpeter in the air with the blood in the lungs; some chemical experiments appear to confirm this idea. But 1. with alkaline salts one gives a reddish color to milk: what reason do we have to attribute the color of blood to saltpeter rather than to alkaline salts? One would be just as justified in saying that lixiviated salt taken from the ground or mixed with nutrients produces the color red, when it comes to be alkalized by the heat of the body: moreover, could one not find in air some mine of alkaline salt, just as one finds saltpeter there? 2. it cannot be proved that there is saltpeter in the air; at the least it is not conceivable that such a large quantity of this salt is to be found in this fluid.

I will not speak here of those who once attributed the redness of blood to the liver; we know that Bartholin stripped it of this faculty; but I believe that one can give back to it in part the functions taken from it; it is not demonstrated that chyle does not pass from the mesenteric veins into the liver; to the contrary, we know that this happens in birds. Experiments even seem to prove that the same thing happens in man.

But how do the united globules take on a red color by this very union? It has been proposed that colors consist of modifications of light; but repeated experiments have demonstrated convincingly that colors were particular to certain rays of light.

The globules in the larges vessels redden all the liquids found there; it is not necessary however that they exist great quantities; one notices that it takes only a little red wine to redden a large glass of water.

Because of the small quantity of red globules, the outer capillaries of arteries are not colored; for as these globules can only pass through these channels one by one, it follows that for one red globule there well be a great quantity of water and lymph, and thus the red color must be absorbed; furthermore, these small globules being compressed, their form must change, and so their color must undergo some change; thus it has been remarked that when passing through the arterial extremities, the globules flatten out and take on a yellowish color; one notices small white diaphanous globules, which are none other than the oily component of the lymph, which do not yet have either enough movement or enough pressure to change color.

Is the redness of blood absolutely necessary? One finds insects that have in their vessels only a white, diaphanous liquid; with this fluid, they live, they make all the movements of which their little muscles are capable.

Blood does not have the same color in all its vessels: if one opens a dog just after it has eaten, one will see that there is in the pulmonary arteries a whitish matter mixed in with the blood ; but in the veins the blood is redder; that follows, clearly, from what we have said. The redness of blood depends on the cohesion of the chyle globules; these globules, because of the pressure exerted on them, were united in the capillary arteries; it is thus necessary that blood be redder in the pulmonary vein than in the artery.

There is yet another difference in color in the blood found in various vessels; arterial blood is very red, but venous blood is blackish; which also follows from what we have established. The redness of blood depends on movement, which, being less strong in the veins, must also produce less effect; but there is a better proof that this difference must occur: the arterial blood is filled with lymph, while the venous blood has none; consequently, red globules are found in greater proportion in the veins, and blood must appear there a darker red, almost black.

When one takes blood from the veins and arteries of the same animal, one notices a difference: blood from the arteries is almost of the same color on the surface and at the bottom; but venous blood is quick blackish at the bottom; I imagine furthermore that this blood was placed into a rather shallow vessel: the difference in color is the result of arterial blood being much more rarefied and mixed than venous blood ; the movement in the arteries, lacking in the veins, must necessarily produce this effect.

Other than the red component of which we have just spoken, are there fibrous components to blood ? There have been anatomists who, rightly, have denied the existence of these parts; but there have been physicians who have answered them with various proofs that there are these sorts of components in blood . See M. Senac, ess. On Physic .

All the components composing blood are agitated by two movements; the circulatory movement of which we have spoken, and the other, internal movement, that is the movement of the sanguinary components in all directions. See Circulation.

This internal movement has not been proved at all, in contrast to circulatory movement; it poses, to the contrary, great difficulty; no one denies that the components making up blood move in different ways within their vessels; their various reflections, the elasticity of the air, the action of the vessels; all of that must imprint diverse movements on the diverse components that make up blood ; but what is denied, is that the internal movement is essential to its fluidity, that is, that blood is fluid because its components are variously agitated: a substance may be quite fluid even though its components are in perfect repose, it suffices only that these components be susceptible to the least impulsion; now, such will be the case when they are not joined. I do not believe that anyone would hold that that the disparateness or the non-adherence of the components of a substance cannot exist without movement; this notion does not cause as many objections as the other, one spares oneself the trouble of looking for the cause of this agitation, that one believes one has found in subtle matter, but that nothing can prove; one cannot conceive of a continual movement in this fluid that carries these components all over, and the reason for this is evident; for, if one wishes to establish movement in all directions, one must say there is no place toward which this fluid does not move; now if such is the case, there will be no moving component that does not find another component moving in its path with equal force; it will thus be unable to move, nor consequently any of the others. Finally, we deny that there exists in blood a principle that itself gives it fluidity, for fluidity depends exclusively on the movement of the vessels; for the clots that one sees in the vessels of a frog exposed to great cold, are not dissolved by the heat communicated to them when one brings the frog close to a fire; but as soon as the movement of the heart increases, the clots divide instantly. The movements of circulation and of fluidity are not the only movements attributed to blood ; a movement of fermentation has also been attributed to it: blood , they say, has acidic and alkaline principles which, continually bumping into one another, must necessarily produce the movement we call fermentation , as happens to liqueurs that have these principles; but as these principles are mixed with sulfurous components that separate them, if follows that the fermentation occurs only little by little; first, some sulfurous components will come out from the juncture of some acids and akalis; second, the same thing will happen to other components; thus the fermentation will take place successively: one can bring forth several more proofs that there is such a fermenting movement in blood . 1. They say that chyle turns into blood ; so, the components of blood change, and the proportion of their principal components is not the same as in the components of chyle; these things, some say, cannot happen without fermentation. 2. Blood is transformed into various humors, and this change is a change in substance, which cannot happen without fermentation. 3. In wheat and oats one finds no urinary salts; yet analyses of the animals who nourish themselves with these substances reveals much of this salt; now, this salt cannot form except by fermentation, no more than can saline salts; all of these arguments are upheld by the analysis of all the liquids of the human body, which one can consult in their individual articles: Saliva, Pancreatic juice, Semen, Urine, etc.

Whatever one says, it is impossible to establish that fermentation occurs in blood ; the various matters that compose it are very oily: now, one knows from chemistry that oil prevents fermentations; vinegar acids that have dissolved lead, and are mixed with much oil, do not boil with alkalis, as analysis has taught us: there are many other examples that I will not report here. 2. There has never been fermentation without rest; now, how does one find such rest in blood , which is carried everywhere throughout the body with great rapidity.

3. But, some will object, how can saline salt form in blood if there is no fermentation? I respond that vinegar acids that have dissolved lead will form saline salt with alkalis; and yet one remarks no fermentation: furthermore, the pressure of the heart and the vessels, and the heat of blood , will introduce acids into the alkalis, and that is sufficient to form a saline salt, etc.

If one accepts all of these arguments, one may prove that there is no need of fermentation to create and maintain the heat of the human body. 1. The solid components of the human body are easily heated by rubbing: one can demonstrate this at any time by the action of the hands or any other component. 2. As soon as the heart begins to act by its alternating movements, it will push against the inner walls of the arteries, which will slowly become hot from their frequent vibrations. 3. The vibrations of the arteries having greatly heated the other solid components, this heat will be communicated to the fluids, thus the solids will be the only cause of heat in the human body. 4. The fluid components in the vessels are quite susceptible to heating, as they are very oily; thus they are susceptible to great heat. 5. From what we have just said, we easily rid ourselves of the obstacle normally presented to this view; that is, the question of how fluids become greatly heated in our bodies without fermentation, given that water never heats up when beaten. One easily sees the explanation in what we have just said; if there were only water in the body, heat would be extinguished, but there are other substances: furthermore, if the walls of the vessels were very strong, and if water did not prevent animal spirits from flowing into the nerves, heat would make itself felt. One has only to place in water pieces of wood that heat easily, one will see that if one rubs them against each other for a long time, they heat up: now, that can happen only if some heat arises in the water contained by the pores; furthermore, if like blood water had the quality of elasticity, heat would similarly arise from the movement of this fluid, as from the movement of blood . 6. There is an experiment that proves that the original cause of circulation and of heat is the action of the vessels. If one takes a frog, opens it and exposes it to cold, one will see that the blood in the mesentery will coagulate and clot. If one approaches these vessels to fire, the clots persist, the action of the igneous components do not resolve them; but as soon as one applies fire to the frog's heart, and it begins to beat, the clots immediately disappear, and circulations begins again, as we have already said. It follows that it is evidently not heat that gives fluidity to blood, that it is only the action of the solid components that divides it; that its heats is an effect of the movement of the vessels, and that it is not even absolutely necessary, as it is only the result of the action of the fibers. If it happened that these fibers had enough force to divide blood , but that they did not have enough to heat themselves, blood would not be the least hot, although it would be fluid. 7. One can see from this that blood , when too agitated by the solid components, will heat even more, will tend to become alkaline, will become more bitter. 8. One can explain why heat becomes stronger when circulation meets with an obstacle: the arteries being more dilated, act with greater force; thus the heat makes itself felt with greater strength. See M. Senac, essays physi.

One can reconcile all that we have just said about blood , with the different types of temperaments established by the ancients. If blood abounds in red globules or those of the first type, this state will be what the ancients called a sanguinary temperament ; and one can explain accordingly the particular symptoms of this temperament. If the red globules are present in small quantities in blood , and if they are fluid and serous, that will be what they called a phlegmatic temperament . If, for whatever reason, blood is overcharged with large components, thick, and difficult to put into motion, the components that the ancients regarded as the principal ingredient of black bile, this will result in the temperament they called melancholic, temperamentum melancolicum . Our food is in general of an acid material, or related to this quality; but by the alterations that it undergoes in our bodies, it quickly passes to a neutral state: the structure of animals' bodies is such that the force of circulation increasingly attenuates the components of blood, corrects their acidity, and animalizes them, so to speak; it makes them volatile and able to pass out through perspiration: it is this same force that disposes them, in the end, to becoming alkaline ; if nothing opposes this transformation, breathing becomes labored and blood corrupt. One sees that bile, before separating from the rest of the mass of blood , undergoes a long circulation: it is one of the most perfect of animal liquids, and the farthest removed from the nature of acids; it is abundant and well conditioned in those whose liquids circulate with force, and whose functions operate smoothly. It is such a constitution, carried to too strong a degree, that justly merits the title given it by the ancients, choleric temperament , or hot and bilious ; the directly opposite constitution, in which circulation is weak and irregular, and movement not strong enough to change the quality of our nourishment, appears to match what the ancients called cachexia , that one can in some way regard as a sort of temperament, and as a disposition that is different from the natural, regular state. It is not, properly speaking, a specific illness, such as would be a bodily disposition that gave rise to a great number of ailments; this constitution is often confused with the phlegmatic temperament, just as the sanguine and bilious temperaments are often found combined in the same subject. One finds in the human body yet other general dispositions that are different from the average state; and these different dispositions may be designated as sulfurous, saline, hot, cold , andc. temperaments, according to the manner in which one considers the diverse components that enter into the composition of blood , their combination, and the different operations of the body. See Heart.

As for the purification of blood , and the manner in which the different liquids are separated, see Secretion.

Concerning the transfusion of the blood of one animal into the veins of another, see Transfusion.

We have in the Philosophical Transactions several extraordinary examples of voluntary hemorrhages; of particular interest is a child who bled from the nose, the ears, and the back of the head for three days. From that time until the sixth day, he bled from the sweat of his head: then, for three days, from the head, the shoulders, and middle of his body. He continued to bleed from his toes, the joints of his arms, and the fingers of each hand, and from the ends of his fingers, until his death. Upon opening his body, small holes resembling the pricks of a needle were found at the places where the blood had exited. See Hemorrhage.

For the manner by which to stop bleeding, see Styptic.

Blood stone, see Sanguine and Hematites.

Bloody hands (having them) is one of the four types of crimes that one can commit on the hunting lands of the king of England. If a man is found with blood on his hands or any part of his body, he is condemned for having killed a wild beast, even when he has not been discovered hunting. See Forest.

Blood rain, see Rain.

Blood flux, see Flux and Dysentery.

Bloody urine , is an illness in which blood is mixed with the urine, in a greater or lesser quantity. See Urine.

Blood that comes out in this way comes from the kidneys, also at times from the bladder or the urethra. This sickness is sometimes caused by a violent emotion, or by falling backward and rupturing some of the urinary vessels: it also sometimes occurs after the sudden suppression of hemorrhoids or menses. Stones, especially kidney stones, can bring on frequent paroxysms of this illness; and cantharides taken internally, or even applied externally without acids, produce the same effect. Blood in urine is a very bad symptom in cases of smallpox and malignant fevers, although in some instances it seems to have served as a crisis, and to have been a sign of the end of the illness.