the nerves which supply a limb be cut, and vital activity be thus arrested, the current of blood will not be darkened; precisely as it will not be brightened in its passage through the lungs, if there be a surplus of carbonic acid in the air. The experiments of Bruch* are very instructive on this point. He found that blood saturated with oxygen became darker in vacuo, while blood saturated with carbonic acid did not change color. What causes the change of color when venous blood is submitted to oxygen? Formerly it was held to be due to the iron in the discs; but the iron may be removed without this removal affecting the phenomenon; so that the opinion now held is, that the change of color is due solely to the difference in the form of the discs, which become brighter as they become more concave, and darker as they become more convex. Oxygen renders them concave, carbonic acid renders them convex. Arterial blood is every where the same: it is one stream perpetually flowing off into smaller streams, but always the same fluid in its minutest rills as in its larger currents. Not so venous blood. That is a confluence of many currents, each one bringing with it something from the soil in which it arises; the streams issuing out of the muscles being substances unlike those issuing out of the nervous centers; the blood which hurries out of the intestine contains substances unlike those which hurry out of the liver. The waste of all the organs has to be carried away by the vessels of the organs. Wondrously does the complex machine work its many purposes: the roaring loom of Life is never for a moment still, weaving and weaving, 'Geburt und Grab, Difficult it is for us to realize to ourselves the fact of this incessant torrent of confluent streams coursing through every part of our bodies, carrying fresh fuel to feed the mighty flame of life, and removing all the ashes which the flame has left. Sudden agitation, setting the heart into more impetuous movement, may make us * Siebold ŭ Kölliker: Zeitschrift für wissenschaftliche Zoologie, iv. 273. Faust. "Birth and the grave, an eternal ocean, a changing motion, a glowing life." aware that it is throbbing ceaselessly; or we may feel it beating when the hand is accidentally resting on it during the calm hours of repose; but even then, when the fact of the heart's beating obtrudes itself on consciousness, we do not mentally pursue the current as it quits the heart to distribute itself even to the remotest part of the body, and thence to return once more- -we do not follow its devious paths, and think of all the mysterious actions which attend its course. If for a moment we could with the bodily eye see into the frame of man, as with the microscope we see into the transparent frames of some simpler animals, what a spectacle would be unvailed! Through one complex system of vessels we should see a leaping torrent of blood, carried into the depths, and over the surfaces of all the organs, at the rapid rate of one foot in every second, and carried from the depths and surfaces through another system of vessels, back again to the heart: yet in spite of the countless channels and the crowded complexity of the tissue, no where should we detect any confusion, no where any failure. Such a spectacle as this is unvailed to the mental eye alone, and we can not contemplate it, even in thought, without a thrill. It is a natural question, and often asked, but difficult to answer, What quantity of blood circulates every minute in our bodies? The many estimates which have been made need not here be given: only those of Lehmann, Weber, and Bischoff now command general attention. Lehmann says that his friend Weber aided him in determining the quantity of blood in two decapitated criminals. The quantity which escaped was thus estimated: Water was injected into the vessels. of the trunk and head, until the fluid, escaping from the veins, had only a pale red or yellow color. The quantity of. blood remaining in the body was then calculated by instituting a comparison between the solid residue of this pale red aqueous fluid and that of the blood which first escaped. The living body of one of the criminals weighed 60,140 grammes, after decapitation, 54,600 grammes, consequently 5540 grammes of blood had escaped; 28,560 grammes of this blood yielded 5.36 of solid residue; 60.5 grammes of sanguineous water, collected * *A Gramme is somewhat more than fifteen grains. after the injection, yielded 3.724 of solid substances. There were collected 6050 grammes of the sanguineous water that returned from the veins, and these contained 37.24 of solid residue, which corresponds to 1980 grammes of blood. The estimate, therefore, turns out as follows: 5540 grammes escaped after decapitation, and 1980 remained in the body, thus making 7520 grammes; in other words, the weight of the whole blood was to that of the body nearly in the ratio of 1 to 8. It is obvious from the account of the experiment that only an approximation could be arrived at. And Bischoff's more recent investigations on the body of a criminal, carefully weighed before and after decapitation, lead to the conclusion that the blood amounted to 94 lbs., or exactly one fourteenth of the whole body.* This nearly corresponds with his former investigations, which gave the weight as one thirteenth of the whole body. If we say ten pounds for an adult healthy man, we shall probably be as near the mark as possible. The quantity, however, necessarily varies in different persons, and seems from some calculations to be greater in women than in men. In the seal its quantity is enormous, surpassing that of all other animals, man included. In former days, blood-letting was one of the "heroic arms" of medical practice; and is sometimes almost appalling to read of the exploits of practitioners. Haller mentions the case of a hysterical woman who was bled one thousand and twenty times in the space of nineteen years; and a girl at Pisa is said to have been bled once a day, or once every other day, during several years. A third case he mentions of a young man who lost seventy-five pounds of blood in ten days: so that if we reckon ten pounds as the utmost which the body contains at any given period, it is clear that this young man's loss must have been repaired almost immediately. In truth, the blood is incessantly being abstracted and replaced during the ordinary processes of life. Were it not continually renewed, it would soon vanish altogether, like water disappearing in sand. The hungry tissues momently snatch at its materials as it hurries through them, and the active absorbents momently pour fresh materials into it. In contemplating the loss of blood from *See his Memoir in Siebold u Kölliker: Zeitschrift, ix. 72. wounds or hemorrhage, and in noting how the vital powers ebb as the blood flows out, we are naturally led to ask whether the peril may not be avoided by pouring in fresh blood. The idea of transfusion is indeed very ancient. But the ancients, in spite of their facile credulity as to the effect of any physiological experiments, were in no condition to make the experiment. They were too unacquainted with physiology, and with the art of experi ment, to know how to set about transfusion. Not until the middle of the seventeenth century had a preparation been made for such a trial. The experiments of Boyle, Graaf, and Fracassati, on the injection of various substances into the veins of animals, were crowned with those of Lower, who, in 1665, injected blood into the veins of a dog. Two years later a bolder attempt was made on man. A French mathematician, Denis, assisted by a surgeon, having repeated with success the experiments of Lower, resolved to extend the new idea. It was difficult to get a human patient on whom the plan could be tried; but one evening a mad man arrived in Paris quite naked, and he was daringly seized by Denis as the fitting subject for the new experiment. Eight ounces of calf's blood were transfused into his veins. That night he slept well. The experiment was repeated on the succeeding day; he slept quietly, and awoke sane! Great was the sensation produced by this success. Lower and King were emboldened to repeat it in London. They found a healthy man willing to have some blood drawn from him, and replaced by that of a sheep. He felt the warm stream pouring in, and declared it was so pleasant that they might repeat the experiment. The tidings flew over Europe. In Italy and Germany the plan was repeated, and it now seemed as if transfusion would become one more of the "heroic arms" of medicine. These hopes were soon dashed. The patient on whom Denis had operated again went mad, was again treated with transfusion, and died during the operation. The son of the Swedish minister, who had been benefited by one transfusion, perished after a second. A third death was assigned to a similar cause; and in April, 1668, the Parliament of Paris made it criminal to attempt transfusion, except with the consent of the Faculty of Paris. Thus the whole thing fell into discredit, to be revived again in our own day, and to be placed at last on a scientific basis. It will immediately occur to the physiologist who reads the accounts of these experiments, that transfusion was effected on the supposition that the blood of all quadrupeds was the same, and that it was indifferent whether a man receive the blood of another man, or of a sheep or calf. This supposition was altogether erroneous. The more rigorous investigations of the moderns have established that only the blood of animals of the same species can be transfused in large quantities without fatal results. The blood of a horse is poison in the veins of a dog; the blood of a sheep is poison in the veins of a cat; but the blood of a horse will revive the fainting ass. From this it follows, that when transfusion is practiced on human beings, human blood must be employed; and so employed, the practice is in some urgent cases not only safe, but forms the sole remedy. Blundell has the glory of having revived and vindicated this practice, and he has seen his idea amply confirmed. Bérard cites fifteen distinct cases of hemorrhage in which transfusion has saved life.t * Seeing that blood has thus a power of reänimating the failing body, it is natural we should inquire to which element of the blood this is due to the cells or the plasma? We know that it is only necessary to withdraw blood from a part, or prevent its access by a ligature round the arteries, and the part gradually loses all its vital properties; but even after the rigor of the muscles announces death, we have only to reädmit the blood by removing the ligature, and the vitality will be restored. Now it has been ascertained that the plasma of the blood, deprived of its cells and fibrine, has no reänimating power when injected, being in fact not more effective than so much warm water. It has also been ascertained that blood, deprived of its fibrine only, produces the same effect as pure blood, whereby it appears that as neither the plasma nor the fibrine possesses the vivifying power, that power must belong to the cells. This is a great step gained, but the restless spirit of * Blundell. แ Experiments on the Transfusion of Blood." Medico-Chirur. Trans. 1818, p. 56. + Berard. Cours de Physiol. iii. 220. It is from this work, and the Leçons of Milne Edwards, that all the details on this subject in the text have been taken. inquiry can not content itself with such a gain, and it asks, what gives to the bloodcells this specific power? Let us see the answer that can be made to such a question. We know that the cells carry the oxygen, either in slight combinations or free, as in vesicles. We know this, because we find that the plasma is unable to absorb much more than one per cent of its volume of oxygen, whereas the blood, containing cells, absorbs from ten to thirteen times that amount. The change of color they exhibit as they take up or give out oxygen, and the fact, that if they are placed in a vessel containing air, they absorb oxygen from that air, whereas the plasma does nothing of the kind, are proofs of the cells being the transporters of oxygen. But this is not all. The experiments of M. BrownSéquard establish the important fact that it is to the oxygen carried by these cells that we must attribute their nutritive agency, and to the carbonic acid carried by them that we must attribute their stimulating agency.* Blood has two offices: it furnishes the tissues with their pabulum, and it stimulates them into activity. Unless the tissues be endowed with certain vital properties, they can not be stimulated into activity; and when stimulated, this activity brings about a destruction, which must be repaired. If stimu lus be applied without equivalent nutrition, the force is soon exhausted. This double office the blood performs, according to M. Brown-Séquard, chiefly through the oxygen, as the agent of nutrition, and of carbonic acid, as the agent of excitation. Without accepting his conclusions in all their absoluteness, we may accept thus much of them, for we see him operating on dead animals, or dead parts of animals, by means of venous blood charged with oxygen, and producing therewith precisely the same effects as with arterial blood; and we see him showing that arterial blood, charged with carbonic acid, acts precisely as venous blood. The conclusion, therefore, is obvious, that the difference between the two fluids is simply owing to the difference in their amounts of oxygen. He takes the blood from a dog's vein, and the blood from its artery, whips both till the fibrine be extracted, and till both have become equally scarlet *Brown-Séquard: Journal de la Physiologie, 1858, i. 91. the first of these conditions, life ceases in spite of the extreme energy of the vital properties, simply because the stimulating power of the blood is insufficient. In the other of these conditions, the stimulating power, being excessive, causes an activity which is soon spent, because it can not be reproduced." Even should we accept to the full the ingenious hypothesis just propounded, we must guard against an exaggeration of its application. Oxygen may be the one chief condition for that exchange between the blood and the tissues which constitutes Nutrition, and without a due supply of oxygen Nutrition may be brought to a stand-still; but we shall greatly err if we suppose that oxidation is itself the process of Nutrition, or that the cells are the sole agents. The albumen, the fats, and the salts which the tissues draw from the blood, are not drawn from the cells, but from the plasma. It is, therefore, quite possible, indeed M. Séquard's experiments render it eminently probable, that the blood-cells, by their oxygen, furnish the indispensable condition of Nutrition, the pabulum being furnished by the bloodplasma. It is also probable that the cells, by their carbonic acid, furnish the condition of nervous and muscular excitement; so that arterial blood, containing more than its usual amount of carbonic acid, causes an excess of the stimulating over the repairing processes. This will account for the greater cerebral excitement succeeded by languor consequent on exposure to the vitiated atmosphere of a theater, a ball-room, or a lecture-room. from the absorption of oxygen. He then injects one of these fluids into the right femoral artery of a dead rabbit, in which the rigidity of death has set in for ten minutes, and the other fluid into the left femoral artery. The result is precisely similar in both limbs, namely, in about five minutes both recover their muscular irritability, which they both retain for twenty minutes. Repeating this experiment with blood drawn from vein and artery, but charged with carbonic acid instead of oxygen, he finds a similar result as to the exciting power. Having thus made clear to himself that, as respects nutrition and excitation, there is no other difference between arterial and venous blood than is assignable to their differences in the amount of oxygen and carbonic acid contained in each; that venous blood, charged with oxygen, acts precisely as arterial blood; and that arterial blood, charged with carbonic acid, acts precisely as venous blood, M. Brown-Séquard proceeds with his demonstration, that unless the blood be highly oxygenated it has no power of nourishing the tissues; and unless it be highly carbonized, it has no power of stimulating them. We can not here afford sufficient space to give any account of the experiments by which these conclusions are reached, and must refer the curious reader to the memoir itself.* But as the idea of the stimulating power of the blood residing chiefly in the carbonic acid, will be novel and startling to most physiological readers, it may be useful to mention one of the experiments. A rabbit was suffocated; and, as usual in such cases, the intestine exhibited very Such is the wondrous fluid we name powerful disorderly movements. Into a Blood, and such its properties, as far as coil of this agitated intestine he injected Science hitherto has learned them. some venous blood highly oxygenated. fore quitting our survey, it will be desiraImmediately the movement ceased. He ble to say a few words respecting the rethen injected arterial blood highly car-lation blood bears to Nutrition, since that bonized, and the movements were at once resumed. Again he injected oxygenated blood, and again the movements ceased, to appear on the second injection of carbonized blood. "It is possible," he says, to produce two conditions of the organism essentially different, one of which consists in the presence of a greater amount of oxygen than usual, both in the venous and in the arterial blood, the other of which consists in the presence of an excess of carbonic acid in both fluids. In Journal de la Physiologie, i. 95. relation is not generally understood. Every one knows that all the tissues are nourished by the blood. But in what way is this effected? Blood, in itself, is perfectly incapable of nourishing the tis sues-so incapable that, if it be poured on them from the rupture of a vessel, it hinders nutrition, and acts like a foreign substance. Accordingly, we see it rigorously excluded from them, shut up in a system of closed vessels; but as it rushes along these vessels, certain of its elements ooze through the delicate walls of the vessels, and furnish a plasma from which the tissues are elaborated. In exchange, | purpose of the individuals; as, for examcertain products of waste are taken up by ple, in the foetus. Thus in the fœtus of the blood, and carried to the organs of the seals, that take the water as soon as excretion. An image may render the they are born, and, I believe, in those of process memorable. The body is like a many other mammals, though removed city intersected by a vast network of from all those conditions against which canals, such as Venice or Amsterdam; hair protects, yet a perfect coat of hair is these canals are laden with barges which formed within the uterus, and before, or carry to each house the meat, vegetables, very shortly after birth, this is shed, and and groceries needed for daily use; and is replaced by another coat of wholly dif while the food is thus presented at each ferent color, the growth of which began door, the canal receives all the sewage of within the uterus. Surely in these cases the houses. One house will take one kind it is only as an excretion, or chiefly as of meat, and another house another kind, such, that this first growth of hair serves while a third will let the meat pass, and to the advantage of the individual." Mr. take only vegetables. But as the original Paget also applies this principle to the exstock of food was limited, it is obvious planation of the rudimental hair which that the demands of each house necessari- exists all over our bodies, and to that of ly affect the supplies of the others. This many other rudimental organs, which subis what occurs in Nutrition: the muscles serve no function whatever. He also, demand one set of principles, the nerves without apparently being aware of Wolff's a second, the bones a third, and each will ideas on this point, applies it to the expladraw from the blood those which it needs, nation of the embryonic phases. "For if allowing the others for which it has no it be influential when all the organs are need to pass on. fully formed," he says, "and are only growing or maintaining themselves, much more will it be so when the several organs are successively forming. At this time, as each nascent organ takes from the nutritive material its appropriate constituents, it will cooperate with the gradual self-development of the blood, to induce in it that condition which is essential, or most favorable, to the formation of the organs next in order to be developed." This principle further enables us to understand how the existence of certain materials in the blood may determine the formation of structures in which these materials are to be incorporated; and it enables us to understand the "constitutional disturbance," or general state of ill-health, which arises from some local disturbance, such as a cold in the head; for, "if each part in its normal nutrition is an excreting organ to the rest, then cessation or perversion of nutrition in one, must, through definite changes in the blood, affect the nutrition. of the rest." How evidently the special condition of the organism determines the growth or decrease of certain organs, may best be seen in the sudden development of the beard and the voice as puberty approaches. Birds in the pairing season acquire their most brilliant plumage, and express the tumult of their emotions in perpetual song. Stags at the same epoch develop their antlers, and make the forest ring with their hoarse barking. Mr. This leads us to notice a luminous conception, attributed by Mr. Paget to Treviranus, but really due to Casper Friedrich Wolff, whose doctrine of epigenesis reposes on it; namely, that "each single part of the body, in respect of its nutrition, stands to the whole body in the relation of a secreting organ." Mr. Paget has illustrated this idea with his accustomed felicity. Every part of the body taking from the blood those substances which it needs, acts as an excretory organ, inasmuch as it removes that which, if retained, would be injurious to the nutrition of the rest of the body. Thus the polypes excrete large quantities of calcareous and silicious earths: in the polypes which have no stony skeleton, these earths are absolutely and utterly excreted; but in those who have a skeleton, they are, though retained within the body, yet as truly excreted from the nutritive fluid and the other parts as if they had been thrown out and washed away. In the same manner, our bones excrete the phosphates from our blood. The hair in its constant growth not only serves its purposes as hair, but also as a source of removal from the blood of the various constituents which form hair." And this excretion office appears in some instances to be the only one by which the hair serves the *Paget: Lectures on Surgical Pathology, i. 24, et seq. |