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tery, 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 carbonised, it has no power of stimulating them. We cannot 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 powerful disorderly movements. Into a coil of this agitated intestine he injected some venous blood highly oxygenated. Immediately the movement ceased. He then injected arterial blood highly carbonised, and the movements were at once resumed. Again he injected oxygenated blood, and again the movements ceased, to appear on the second injection of carbonised 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 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 cannot 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 blood-plasma. 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 theatre, a ball-room, or a lecture-room.
Such is the wondrous fluid we name Blood, and such its properties, as far as Science hitherto has learned them. Before quitting our survey, it will be desirable to say a few words respecting the relation blood bears to Nutrition, since that 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 tissues-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
* Journal de la Physiologie, i. 95.
of the vessels, and furnish a plasma from which the tissues are elaborated. In exchange, certain products of waste are taken up by the blood, and carried to the organs of excretion. An image may render the process memorable. The body is like a city intersected by a vast network of canals, such as Venice or Amsterdam; these canals are laden with barges which carry to each house the meat, vegetables, and groceries needed for daily use; and while the food is thus presented at each door, the canal receives all the sewage of the houses. One house will take one kind of meat, and another house another kind, while a third will let the meat pass, and take only vegetables. But as the original stock of food was limited, it is obvious that the demands of each house necessarily affect the supplies of the others. This is what occurs in Nutrition: the muscles demand one set of principles, the nerves a second, the bones a third, and each will draw from the blood those which it needs, allowing the others for which it has no need to pass on.
This leads us to notice a luminous conception, attributed by Mr Paget to Treviranus, but really due to Caspar 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 which 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 purpose of the individuals; as, for example, in the fœtus. Thus in the foetus of the seals, that take the water as soon as they are born, and, I believe, in those of many other mammals, though removed from all those conditions against which hair protects, yet a perfect coat of hair is formed within the uterus, and before, or very shortly after birth, this is shed, and is replaced by another coat of wholly different colour, the growth of which began within the uterus. Surely in these cases it is only as an excretion, or chiefly as such, that this first growth of hair serves to the advantage of the individual." Mr Paget also applies this principle to the explanation of the rudimental hair which exists all over our bodies, and to that of many other rudimental organs, which subserve no function whatever. He also, without apparently being aware of Wolff's ideas on this point, applies it to the explanation of the embryonic phases. "For if it be influential when all the organs are 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 co-operate with the gradual self-development of the blood, to induce in it that condition which is essential, or most favourable, 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 stitutional 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
* PAGET: Lectures on Surgical Pathology, i. 24, et seq.
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 Paget justly says " Where two or more organs are thus manifestly connected in nutrition, and not connected in the exercise of any external office, their connection is because each of them is partly formed of materials left in the blood on the formation of the other."*
Does not this throw a new light upon the blood? and do you not therein catch a glimpse of many processes before entirely obscure? It assures us that the blood is not "flowing flesh"--la chair coulanteas Bordeu called it, to the great delight of his successors; nor is it even liquid food. It is an organic structure, incessantly passing through changes, which changes are the conditions of all development and activity. The Food and Drink which we take become subjected to a complicated series of digestive processes. The liquid product of Digestion is carried into the blood-stream, undergoing various changes in its route. It is now blood; but other changes supervene before this blood is fitted for the nourishment of the tissues; and then certain elements pass from it through the walls of the capillaries to be finally assimilated by the tissues. In the simpler animals, the liquid product of digestion is itself the immediate agent of Nutrition, and does not pass through the intermediate stage of blood. It escapes from the digestive canal into the general substance of the body, which it per
* PAGET, p. 32.
meates and nourishes much in the way that the blood-plasma nourishes the substance of the more complex animals. But in the simplest animals there is not even this approach to blood. There is no liquid product of digestion, for there is no digestion at all, the water in which these animals live carrying organic matter in solution; this permeates the substance, and is assimilated: thus does the water play the part of blood, carrying the food, and carrying away the waste.t
Let the speculative eye traverse the marvellous scale of created beings upwards, from the simplest to the most complex, and it will observe that Assimilation first takes place by the direct relation of the organism to the surrounding medium; next arrives the interposition of agencies which prepare the food for the higher effects it has to produce, and instead of relying on organic substances in solution, the organism is seen extracting nutriment from other organisms; finally is seen the operation of still more complicated agencies, which impress on the digested food still higher characters, converting it into blood. This blood is retained in a system of vessels everywhere closed. Yet, in spite of the absence of orifices or pores, it is distributed impartially to the most distant parts of the organism, and it is distributed according to the momentary requirements of each part, so that when an organ is called upon to put forth increased energy, there is always an increase of food sent to supply that energy. If the stomach has been quiescent for hours while the brain has been active, the regulating power of the circulation has adapted the supply of blood to each organ; and no sooner will the stomach be called upon to exert itself, than an abundant supply of blood will instantly be directed to it. This simple and beautiful fact in the animal economy should warn men against the vicious habit of studying at or shortly after meals, or of tasking the brain when the stomach is also tasked.
+ This was shown at length in a former number of Maga, June 1857.
THERE are few things so strange, arbitrary, and unaccountable, as that amount of common liking and regard which we call popularity. Sometimes it answers to the touch of real genius, with a unanimity and readiness which, for the moment, might prompt us to believe in its decision as the true and infallible test of reputation; but ere we have had time to do more than observe the instinctive and universal impulse of this recognition, the popular fancy has gone mad after some silly wonder, or raised to its highest honours some superficial and worthless production, which we should have supposed incapable of moving to any sentiment whatever any single human mind. Nothing can possibly be more puzzling than this strange perversity. The applauding clamour of the vox populi-let disappointed men say what they will is, after all, the culmination and apotheosis of fame. Yet the same clamour rushes with unreasoning lavishness after books and persons which have no more claim to fame, than has the smallest newspaper critic who professes to dispense it. In the world of books one has but to glance over the title-pages of those which bear the honours of many editions, to perceive the extraordinary freaks of this popularity, which bestows upon the most frivolous and commonplace performances applause as great as that with which it celebrates the most eminent works of genius. This fantastic uncertainty leaves us totally unable either to receive or to deny the authority of a popular success. It may be bravely won and honestly deserved a triumph of real and genuine art; or it may be a haphazard "hit," which it is impossible to give any reason for, and at which authors and readers are alike astonished; but so purely unaccountable are the vaticinations of this oracle, that no one is justified in making a general conclusion as to the worth or worthlessness of its verdict. It is folly to say, on the
one hand, that the highest productions of genius are unappreciated by the multitude; and it is still greater folly, on the other, to make success an infallible proof of desert. decisions of the popular tribunal of literary criticism, are not at all unlike the decisions of that jury which regulated its verdicts on the purely impartial principle of alternation, and said guilty and not guilty time about, with a noble indifference to such small matters as facts or evidence. If we are disappointed of the verdict ourselves, we cannot console our mortification by the thought that it is always in the wrong, and never justly rewards a generous ambition: but that it is perfectly capricious, unreasoning, and unexplainable; that it is simply impossible to form any conclusion beforehand as to what its judgment may be; and that, often right, it still preserves a delightful independence, and keeps resolutely clear of the imputation of being always so, nobody acquainted with modern literature or opinions ever deny.
It is impossible to avoid thinking this, when one contemplates the enormous amount of good books current and popular at the present time -we might add of bad books alsofor the religious and the irreligious are almost equally independent of those ordinary qualities which achieve the rewards and honours of literature.
But we will not compare the penny novels, disreputable and unfragrant, with those trim octavos and duodecimos which throng the tables of religious publishers, and pass by the thousand into homes of respectability. These pious volumes are, for the most part, as excellent in intention as they are important in subject-they are, indeed, only too much bent upon the universal edification of their audience, and are reluctant to record the merest passing incident without weighing it down with the heavy overbalance of a spiritual lesson. When we say pious volumes, we beg that no one will suppose we mean to imply the faintest approach
to a scoff. Their piety is the only genuine quality in the great mass of these publications; and we must presume it is for that sole sake that many really prefer, and many more think it right to receive, works which have scarcely a claim to be called literature, save the mere fact that they have been written and are printed. Their piety alone might induce us to pass over without comment the other imperfections of this class of writing; but we cannot suppose that it is any real advantage to the religious community to put up with these publications, out of tenderness for the sentiment of godliness which is presumed to pervade them. This has been, perhaps, done too much already. We have been afraid to incur the reproach of a want of spiritual appreciation, and a general dislike to religious writings, and so have been obliged to swallow the endless repetition, and flat and unnatural representations of life, conveyed to us in books which nothing but their piety could have entitled to a moment's consideration. This is rather hard upon the unfortunate critic: he reads, because he respects the religious feeling of the writer; he condemns, because human nature cannot stand the manner of the performance; and he is immediately set down as a profane person, who cannot be supposed to appreciate the true beauty of holiness. Perhaps this hard dealing is one of the reasons why the common mass of religious literature is so destitute of ordinary literary qualities for men who love the matter have been afraid to incur the odium of criticising the manner of those productions, and the censorship has been left to hands indifferent, and passed by with a sneer or a laugh according to the temper of the moment. Yet it is impossible to overestimate the importance of this kind of writing. For one thing, it conveys to many a totally erroneous idea of religious people, and of the effects of personal godliness, which is a great misfortune; and it cannot fail to depreciate the cultivation, refinement, and good taste which we fondly expect must accompany our outside progress and increasing comfort; for there is no
class of books so largely sold, and so universally possessed. The most famous fictions of the day are in less demand than those pieces of religious biography of which, were the names struck out, one might read a score without being able to tell where one terminated and another began; and neither Thackeray nor Dickens can count half as many editions as have fallen to the lot, for example, of the Memorials of Captain Hedley Vicars -a little volume fully representing the character of its kind. We do not approach this subject with either contempt or levity-far from that, we speak sadly, knowing that we shall be obliged to condemn what hundreds of better people than we applaud and love; yet it does seem so strange an enigma why the greatest subjects in the world should be treated with the poorest language; why lives which, in the living, were noble, generous, and above praise, should become, in the telling, only tiresome and tedious; and why multitudes, great enough to convert private applause into general popularity, should be pleased to have it so- -that we cannot refrain from inquiring why and how this strange paradox is? We beg to premise, however, in the first place, that we entirely leave out legitimate sermons, and all the effusions of all the authorised teachers of all the churches. What we have to deal with is specially the crowd of pious memoirs, the floating light (or heavy) literature of the religious world.
Memoirs of pure minds, of noble lives, of hearts warm with all the fervour and sunshine of the Gospel
let us do homage to those young saints, those virgin confessors, those true soldiers of our Lord. It is no reproach to them that friends make merchandise of their devout letters, their pious sayings, and the secret life which they lived with God-or that an unwise love beguiles its grief by making into talk, and throwing irreverently open, the innermost sanctuary of their souls. They are the greatest sufferers by the operation. Yet it is wonderful to perceive with what ease all features of human individuality can be obliterated from the record which professes to tell us how one and another, real men and