it has recently been demonstrated by the conjoined efforts of Traube, Heidenhain, and Donders, and still more distinctly by Fick and Wislicenus, Frankland and Parkes, that the oxidation of nitrogenous substances cannot account for nearly all the work done in the body. Traube, indeed, has started a rival hypothesis, which has been accepted by Fick and Wislicenus in their celebrated memoir;* namely, that the oxidation of muscle contributes nothing whatever to muscular power, but that the whole of the latter is derived from the oxidation of non-nitrogenous bodies, such as fats and the so-called hydrates of carbon. But as they agree with Liebig in placing the seat of this oxidation in the tissue, there is no great difference, as far as the blood is concerned, between the two views. But are there, indeed, two distinct kinds of oxidation going on in the body, one inside and one outside the walls of the blood-vessels ? Is it probable, or indeed possible, that sufficient oxygen can pass out through the thin walls of the capillaries to account for the enormous force exerted by the body in twenty-four hours? Mayer thought not, and argued against the notion in his immortal treatise, "Organic Motion in its connection with Change of Matter," published more than twenty years ago.t I believe he was right in this, as in so many other things, and I have elsewhere drawn attention to his arguments, and endeavoured to add others to them. The question is one of immense theoretical and practical importance, and I will therefore enter into it in some detail. To begin with, it is necessary to bear in mind another wellknown and most important function of the blood. All the tissues of the body, the muscles among the number, are subject to a ceaseless process of disintegration and destruction. The elementary parts of which a tissue consists, have a definite term of life. They are born, grow, decay, and die, having previously developed new germinal matter from which their successors arise. There is no doubt about this, and it is equally certain that the nutrient matter, the pabulum, from which the new parts are formed and nourished, is derived from the blood, some portion of which must travel through the thin walls of the capillaries, and irrigate the tissue. Extreme uncertainty exists as to the mode in which this exudation takes place. At first sight it would appear to be simply a question of liquid diffusion; but, apart from the colloidal nature of the albuminous bodies of the blood, there are some striking points of difference between the composition of the blood and that of "On the Origin of Muscular Power," "Phil. Mag.," June, 1866 (Supplement). +"Die Organische Bewegung in ihrem Zusammenhange mit dem Stoffwechsel." Heilbronn, 1845. "Phil. Mag.," May, 1867. the muscular juice, in respect even of some of the most diffusible substances. Thus common salt, an extremely diffusible compound, is found in large quantity in the blood, but is almost entirely absent in muscular juice, and the blood is invariably and necessarily alkaline; whereas the liquid of the tissue is acid, and may even contain, as Liebig has remarked, enough acid to neutralize the blood. Probably the pressure under which the blood flows, influences in some manner the exudation, but it would be vain to pretend that it explains it.* The excess of the nutrient fluid, together with the products of the disintegration of the tissues, returns to the blood, a portion perhaps direct to the capillaries, but the great bulk, in all probability, through the lymphatics, which seem to act as overflow-pipes to the tissues. Mayer therefore suggested that the quantity of lymph might be taken as a measure of the quantity of fluid exuded in a given time. Bidder and Schmidt estimate the lymph returned to the blood in twenty-four hours at 22 lbs., but it is safer to assume it to be at least 30 lbs. It would hardly do, however, to take even this quantity as a representation of the average exudation through the capillary walls in twenty-four hours, and I have thought it right to treble it, so as to have a decided over-statement of its probable quantity. We thus get 90 lbs. a day, or about 40 litres. Now if oxygen leaves the blood and passes into the tissues, it is evident that it must pass in solution in this 40 litres of exudate. How much oxygen could possibly be dissolved by this 40 litres? There is every reason to believe that the exudate does not differ materially from liquor-sanguinis in composition, and we have before seen that liquor-sanguinis is about equal to water in its power of dissolving oxygen. 40 litres of water would dissolve less than two grammes of oxygen; and this quantity of oxygen, whether it were employed in the oxidation of muscle, of fat, or of sugar, could not yield as much as 3000 metre-kilogrammest of force. But it may be urged that, though unlikely, it is still possible that the exuding fluid may be able to carry with it a larger proportion of oxygen than this. Be it so. Let us make the absurd assumption that every hundred volumes of exudate contains more oxygen than the arterial corpuscles themselves, do, when saturated with the gas. If each hundred volumes of exudate contained forty volumes of oxygen, 40 litres would still only contain about 23 grammes, and this, in uniting with oxidizable * Some of these arguments were suggested to me by Dr. Marcet, F.R.S., who has studied the bearings of dialysis on pathology with great care and success. A metre-kilogramme is the force required to raise one kilogramme one metre. It is equal to about 7 foot-pounds, and is now almost universally employed as the measure of force. materials, could only yield about 30,000 metre-kilogrammes of force. Now the daily work of the heart alone is estimated by Donders at 86,000 metre-kilogrammes, and it is an extreme under-statement to assert that the total daily work of the body in health is 100,000 metre-kilogrammes. To do even this quantity of work, twice the quantity, or 200,000 metre-kilogrammes of force must, as Heidenhain has proved, be provided; so that even taking the highest possible calculation of the quantity of oxygen which could pass into the tissues, we sce that it cannot account for one-sixth of the work done in them. It is more probable, indeed, that it cannot account for one-sixtieth. To supply the minimum force per diem exerted in the body, there must be a daily exudation of about 264 litres, or -ton, if the exudate contains as much oxygen as arterial corpuscles; or, 3500 litres, or 3-tons, on the more probable supposition that it will not dissolve more than water will. These figures appears to me to furnish a complete answer to the current tl eory of tissue-oxidation, and to force us inevitably to the conclusion so clearly pointed out by Mayer, namely, that the whole, or nearly the whole, of the animal oxidation, is effected in the blood itself, and consequently that there must exist some provision by which chemical force set free inside a capillary is converted into mechanical work in the tissues outside of it. This view of the nature of animal oxidation tends to define more clearly our knowledge of the functions of the blood. Nutrition is one of its functions. It carries with it in its course the appropriate pabulum for the repair of all the tissues of the body. Bones, nerves, glands, and muscles, all alike reproduce their elementary parts at the expense of material derived from its fertilizing stream. And as these elementary parts attain their term of life they decompose and liquefy, passing again into the blood, for the most part through the same lymphatic vessels which take back the excess of the nutritive fluid. In the lymphatic vessels and glands much of the lymph is once more organized into blood, but the products of the disintegration of tissue are probably incapable of this renewal, and, in the absence of evidence must be supposed to return into the blood in an unorganized condition. Equally important with the foregoing is the function of oxidation, to which the force as well as the heat of the body is due. Nitrogenous as well as non-nitrogenous bodies are oxidized in the blood, and though we do not yet know the precise conditions or the precise mode in which the oxidation is effected, we are justified in inferring that it is by the direct agency of the corpuscles. There is on this view no ground for the assumption that either force or heat is due exclusively to the oxidation of one or the other class of organic compounds. Both are oxidized, and one is as likely as the other to be the motive power. Even the muscle itself, inasmuch as it is finally oxidized in the blood, may give rise to muscular work, and we must therefore conclude that Traube's hypothesis is as much an over-statement on the one side as Liebig's was other. on the The changes effected by the blood in the exercise of its functions are subject, to a most remarkable extent, to the control of the nerves; and little as we know of this the most obscure region of physiology, we cannot avoid the conclusion that they are directly concerned in the transformation of chemical force into mechanical effect. The muscular currents of electricity, which have been so carefully studied by Du BoisReymond, Helmholtz, Heidenhain, and many others, are, no doubt, closely connected with this conversion; but I will abstain from speculations which are apt to degenerate into bare guesses. Dim foreshadowings of great discoveries lie before us, and it is better, after clearly stating to ourselves the truths already established, or made probable, to wait with humility, watching til diligent and patient search shall have been rewarded with fresh unveilings. If we can clear a point or two in the intricate forest of knowledge which lies before us, we shall have done truer work than by any amount of speculation. THE LUNAR CLEFTS-MARE VAPORUM-JUPITER'S SATELLITES-OCCULTATIONS. BY THE REV. T. W. WEBB, A.M., F.R.A.S. IN our last paper we followed the Great Cleft as far as the crater Hyginus: we now proceed to give the results of the observations of B. and M. upon its future course; referring at the same time to the diagram in our last number. This erater, 3 miles in diam., and tolerably deep, with 6° or 7° of brightness, has its ring split by the cleft, which passes across the interior, with elevated edges, in such a manner that the continuity of its banks is nowhere interrupted. Of this they had an interesting proof upon one occasion in the waning moon, when the steady air admitted of a power of 300: the interior of the crater was wholly in shade, with the exception of two minute but very brilliant lines of light in the position of the cleft, while the wall on the N.E. and W., where the cleft encountered it, was interrupted by a very narrow but perfectly black shadow. From the E. side of Hyginus issues an extremely small cleft, 4 or 5 miles in length, which was detected by Lohrmann, and seen, once only, by B. and M. After leaving this spot, the cleft, in its westward course, touches on five extremely small craters, or possibly only "longish circular widenings," and is bordered on the S. by two broad flat hills; all these being objects of an exceedingly difficult character. Beyond the tenth crater the cleft becomes wider, flatter, and less regular, and ends as it began, at a long hill, at whose S.W. extremity a little crater (Agrippa b) is faintly perceptible. Its whole length is about 106 miles, its average breadth nearly 1 mile the steeper are the more reflective parts; the light of the flatter ends losing itself in that of the surrounding surface. With the great achromatic at Dorpat, M. subsequently found that a great part of this cleft consisted of a chain of confluent roundish cavities. The plain S. of the cleft contains a few small craters of various sizes, two small dark spots and one larger, and one of a green hue, about 3° in brightness, and extending over about 3,600 square miles. On the N. the cleft is attended by a number of very low parallel chains of hills; one mass immediately N. of Hyginus shows a curious spiral arrangement; but generally they point S.W. or S.S.W., and this bearing is visible over a considerable area in this direction, overspread with minute banks and ridges, invisible excepting near the terminator, and usually only from 40 to 60 yards in height. Our authorities especially direct attention to the fact that in this region, where no deception can be |