"Till about five years ago, or somewhat more, I saw a letter from Gabrielle Desmarets, and "Ah! which made you suspect, as I do, that the child is Gabrielle Desmarets' daughter." Arabella reared her crest as a serpent before it strikes. "Gabrielle's daughter! You think so. Her child that I sheltered! Her child for whom I have just pleaded to you! Hers!" She suddenly became silent. Evidently that idea had never before struck her; evidently it now shocked her; evidently something was passing through her mind which did not allow that idea to be dismissed. Darrell was about to address her, she exclaimed abruptly, "No! say no more now. You may hear from me again should I learn what may decide at least this doubt one way or the other. Farewell, sir." As "Not yet. Permit me to remind you that you have saved the life of a man whose wealth is immense." "Mr Darrell, my wealth in relation to my wants is perhaps immense as yours, for I do not spend what I possess." 'But this unhappy outlaw whom you would save from himself can henceforth be to you but a burthen and a charge. After what has passed to-night, I do tremble to think that penury may whisper other houses to rob, other lives to menace. Let me, then, place at your disposal, to be employed in such mode as you deem the best, whatever may be sufficient 66 No, Mr Darrell," said Arabella, fiercely; "whatever he be, never with my consent shall Jasper Losely be beholden to you for alms. If money can save him from shame and a dreadful death, that money shall be mine. I have said it. And, hark you, Mr Darrell, what is repentance without atonement? I say not that I repent; but I do know that I seek to atone. The iron-grey robe fluttered an instant, and then vanished from the room. When Alban Morley returned to the library, he saw Darrell at the farther corner of the room, on his knees. Well might Guy Darrell thank Heaven for the mercies vouchsafed to him that night. Life preserved? Is that all? Might life yet be bettered and gladdened? Was there aught in the grim woman's words that might bequeath thoughts which reflection would ripen into influences over action?-aught that might suggest the cases in which, not ignobly, Pity might subjugate Scorn? In the royal abode of that soul, does Pride only fortify Honour?- is it but the mild king, not the imperial despot? Would it blind, as its rival, the reason? Would it chain as a rebel the Heart? Would it mar the dominions that might be serene by the treasures it wastes-by the wars it provokes? Self-knowledge! selfknowledge! From Heaven, indeed, descends the precept-" KNOW THYSELF." That truth was told to us by the old heathen oracle. But what old heathen oracle has told us how to know? ANIMAL HEAT. A BIRD-CAGE hangs above a small aquarium; in the cage there is a bird; in the glass tank, seaweeds, zoophytes, molluscs, and fish. The atmosphere of the apartment varies with the variations of temperature which accompany the earth's daily rotation and annual movement. The summer sunlight streams in through the windows; the icy north wind rushes through the crevices; the shadows of night and the evaporations of morning bring with them perpetual risings and fallings of the temperature of that room; and with these risings and fallings there are corresponding fluctuations in the temperature of the glass and water of the tank, the brass and woodwork of the cage. This is according to the law by which an equilibrium of temperature is always established among inorganic bodies. The warmer atmosphere rapidly warms the glass and water-the cooler atmosphere rapidly cools them; it is true that the water will always be somewhat colder than the atmosphere, because it loses heat in evaporation, but nevertheless, as the external temperature rises and falls, that of the water also rises and falls. While these changes, so familiar and so easy of explanation, have been taking place, the bird has been neither colder nor warmer; throughout the fluctuations of external temperature it has preserved almost uniformly the very high degree of warmth which, as a bird, belongs to it. Neither the beams of an August sun, nor the nipping east of December, have raised or lowered its normal heat more than one or two degrees. You may perhaps imagine that it has been kept warm through the winter by its envelope of feathers, but this is true only to a very slight extent; strip it of its feathers, and you will still find its heat greatly above that of the air; whereas, if a heated substance be enveloped in feathers, and left exposed to the air, it will soon become as cold as the air. Driven from this explanation, you will ask, How is it that the bird is enabled to preserve a steady temperature of a high degree amid unsteady influences from without? The answer is obviously to be sought in the organism and its processes, not in any external influence; and a certain Philosophy, somewhat rash and ready, fond of phrases and impatient of proof, will assure you that the bird, as an organised being, is absolved from the law of equilibrium which rules all inorganic bodies, because the bird is endowed with a "vital principle which suspends the action of physical laws." This explanation, which to many has seemed satisfactory, labours under two disadvantages-first, that it invokes the operation of a "vital principle," of which we can form no definite conception; and secondly, that the assumed suspension of physical laws is a pure figment. The organism, living or dead, radiates heat with equal facility; but when living, it produces heat to compensate the loss; and when dead, it no longer produces heat, so that it speedily becomes as cold as the external air. The processes of Life do not suspend the operation of physical laws, although, by the introduction of more complex conditions, they bring about results which, superficially considered, look like a suspension of those laws. A close analysis always detects the physical laws. No one thinks of attributing to a spirit-lamp, when lighted under a vessel of water, the power of suspending the equilibrium of temperature, because it keeps the water boiling in spite of the constant loss of heat by evaporation. Without the lamp, the boiling water would speedily cool below the temperature of the air; with the lamp, it may be kept indefinitely at the boiling point, if fresh water be from time to time added to replace what has evaporated. There is no "lamp-principle" suspending physical laws. Nor is there any mysterious agent in Animal Heat. Just as the temperature of the water is kept constant by the continual reproduction of heat equal ling the amount lost, so is the temperature of the bird kept constant by a continual reproduction of heat within; and although the vital processes by which that reproduction is effected are very far from exhibiting the simplicity of the spirit-lamp, and are indeed still involved in great obscurity, yet we know that physical laws are in no sense suspended thereby, and that the living animal has the tendency to establish an equilibrium between its temperature and that of the objects surrounding it. Even in the microscopic animalcules such a supply exists. We might assume this a priori, but we can establish it experimentally, for if water be gradually frozen under the microscope, it will be seen that the last drops which solidify are those which surround the animalcules, and have been kept liquid by their heat. Organic beings are thus distinguishable from inorganic in possessing, as a necessary consequence of their vital activity, a self-supplying source of heat; and organic beings are distinguishable among each other by the rapidity with which this heat is supplied, and the facility with which it is radiated, and not, current classification implies, into animals with warm blood, animals with cold blood, and plants with no heat at all. There are no animals with cold blood, and all plants produce heat. But plants, except during their periods of germination and flowering, when they are sensibly warmer than the air, produce heat so slowly, and part with it so easily, that their temperature always follows that of the medium in which they live; and the so-called "cold-blooded animals" produce heat so slowly that they are never more than two or three degrees above the medium, and sometimes even below it, owing to the rapidity of evaporation from their surfaces. Insects-bees, for instance We have only to extend our investigations and examine the temperature of the other organised bodiesseaweeds, zoophytes, molluscs, and fish-during these changes which seem not to have affected the bird, to find that this mysterious "vital principle" suddenly fails altogether. It here abdicates its autocratic power. It suspends no laws, but permits equilibrium to be established unopposed. The seaweeds are as cold as the water, and get warmer as the water warms. The zoophytes have no appreciable superiority of temperature. The fish are only two or three degrees warmer. Either we must give up the explanation which the vital principle seemed to afford, or we must deny that the coldblooded animals, as they are called, have any vital principle at all. In vain will a refuge be sought in the greater cooling agency of water over-produce heat with a rapidity equal that of air; for although something must be allowed for this, we cannot by it account for the enormous disproportion between the temperature of the fish and the bird ; and for these reasons: The Bonito, equally subject to this cooling agency of water, preserves a constant temperature of 20° above the sea; and the temperature of the Narwhal is nearly that of man -namely, 96° Fahrenheit. Moreover, while some marine animals are thus independent of thetemperature of water, serpents, lizards, and frogs are dependent on the temperature of the air. It may be laid down as an axiom, that every living organism has within it a source of self-supplying heat. The amount of heat thus supplied will depend on the amount and nature of the chemical changes which take place within the organism, to that of birds; but they part with it so rapidly that their temperature is little above that of the air. When bees are collected together in the hive, the heat thus radiated is seen to be very great. Many writers object to the old distinction of warm and cold-blooded animals, as unphysiological, and suggest that the distinction should be, that the warm-blooded are independent and the cold-blooded dependent on the external temperature; the one class preserving its normal heat under all variations of the external medium, and the other class growing warmer and colder as the external medium rises and falls. But against this distinction we would urge three arguments. First,-Both classes of animals are dependent on the external temperature, and both are independent of it; they are dependent, because it accelerates or retards their vital activities by which their own heat is evolved; they are independent, because whatever may be the amount of external heat or cold, their own temperature, being really evolved in their vital processes, is always restrained within certain limits, and is almost always somewhat above that of the external medium,* until a limit is reached, and then, if the external temperature continue to increase, they perish, or their heat falls below that of the medium. Secondly, The young of many warmblooded animals are as much dependent on external temperature as frogs and fish; and even the adult animals of the hybernating class are in this category: no sooner does the external temperature fall, than their heat sinks, and this depression continues till they are only three degrees warmer than the air. Thirdly,-While the foregoing arguments have shown that the distinction is not tenable in the presence of facts, we would further remark that, granting the distinction to be valid, the cause would still have to be sought, and we should ask, why one class of animals was independent and another dependent on the external temperature? In fixing attention on the physiological differences of rapid supply and rapid radiation, as the real ground of distinction, we avoid the objections just brought forward; at the same time, inquiry into the cause of animal heat is disengaged from many a perplexing digression. The marvellous balance between supply and loss exhibited by the human organism, and indeed by that of most warm-blooded animals, may be best seen in the following facts. Our temperature is 98°, and this is the standard, no matter what may be the external heat. In the tropics, the thermometer during several hours of the day is 110°. In British India it is sometimes as high as 130°. In the arctic zones it has been observed by our voyagers as low as 90°, and even 102°, below freezing-point. Nevertheless, amid such extensive variations of the external temperature, that of the human organism has but slightly varied, and a thermometer placed under the tongue of an arctic voyager will show the same degree of heat as one under the tongue of a soldier before the walls of Delhi. Throughout the scale of 200° which represents the variations of climate borne by our voyagers and soldiers, the average temperature of the human organism remains steady at 98°. We say average, because the same man is not always at the same degree; his temperature varies at different seasons, different hours, and under different conditions; and of course different men vary among themselves. Dr Livingstone remarks, "If my experiments are correct, the blood of an European is higher than that of an African. The bulb of the thermometer held under my tongue stood at 100°; under that of the natives at 98°."+ This is most likely nothing more than an individual difference; but the point is worth investigating. Although the organism can endure a heat greater than its own, yet this would soon be fatal if continued. For a short period the excess of temperature can be resisted; and it is astonishing what a power of resistance we possess. Chabert, the once celebrated "Fire-King," who used to exhibit in public, amazed his audience by entering an oven, the heat of which was from 400° to 600°; and although we have no details as to his own temperature when subject to that heat, we may be sure that it could not have risen many degrees above 98°, otherwise he would have perished; for the experiments of Berger and Delaroche prove, that when the temperature of animals is raised 11° or 13° above the normal standard they perish. Workers in iron-foundries and gasworks are constantly obliged to remain for some time in air which is as high as 250°, yet their own temperature remains * We found the temperature of a lizard to be 56° in the mouth when the air was at 54°. + LIVINGSTONE's Travels in South Africa, p. 509. ‡Quoted by W. EDWARDS, De l'Influence des Agens Physiques sur la Vie. tolerably uniform. A dog confined in a heated chamber at 220°-236°, in which he remained half an hour, was found to have gained only 7°; and while the external temperature stood as high as 236°, his own stood only at 108°. It thus appears that warm-blooded animals, besides their central source of heat, which keeps up their temperature in spite of external cold, have also a cooling apparatus by which their standard of heat is preserved in spite of excessive heat outside. What is this process, which prevents the equilibrium of heat, and can keep the animal temperature more than one hundred and fifty degrees below that of the atmosphere? We can easily understand why a kettle of water can be kept at boiling-point in a cold atmosphere, so long as a flame is underneath it; but what is it which can keep that water cold when the temperature of the air is many degrees above boiling-point? A man whose temperature is 98° in an atmosphere of 60°, suddenly steps into an atmosphere of 200°, and yet his own warmth is scarcely elevated. The ordinary explanation of this surprising fact is, that the evaporation and exhalation of vapour and water from the surface are so accelerated by the excessive heat, that they suffice to keep the man's temperature from rising. Let us look more closely into this. All over the surface of our bodies there are scattered millions of minute orifices which open into the delicate convoluted tubes lying underneath the skin, and are called by anatomists sudoriparous glands. Each of these tubes, when straightened, measures about a quarter of an inch; and as, according to Erasmus Wilson, whose figures we follow, there are 3528 of these tubes on every square inch of the palm of the hand, there must be no less than 882 inches of tubing on such a square inch. In some parts of the body the number of tubes is even greater; in most parts it is less. Erasmus Wilson estimates that there are 2800 on every square inch, on the average; and as the total number of such inches is 2500, we arrive at the astounding result that, spread over the surface of the body, there are not VOL. LXXXIV.—NO. DXVI. less than twenty-eight miles of tubing, by means of which liquid may be secreted, and given off as vapour in insensible perspiration, or as water in sensible perspiration. In the ordinary circumstances of daily life, the amount of fluid which is thus given off from the skin (and lungs) during the twenty-four hours, varies from 13 lb. to 5 lb.; under extraordinary circumstances the amount will of course rise enormously. Dr Southwood Smith found that the workmen in the gasworks employed in making up the fires, and other occupations which subjected them to great heat, lost on an average 3 lb. 6 oz. in forty-five minutes; and when working for seventy minutes in an unusually hot place, their loss was 5 lb. 2 oz., and 4 lb. 14 oz. Whatever stimulates the circulation of the blood at the surface will necessarily increase the action of the sudoriparous glands. A warm atmosphere or a warm bath immediately causes the surface-circulation to be increased. Muscular exertion does the same. That the ordinary amount of evaporation and exhalation will be greatly raised on our entrance into an atmosphere of 200° is very certain; but the question is, whether this amount, be it never so considerable, is sufficient of itself to account for the enormous difference between the temperature of the animal and that of the atmosphere? We must remember that not only is the animal more than 100° lower than iron or wood in such an atmosphere, but it is this amount lower in spite of the incessant production of heat taking place in his own organism, by the chemical changes on which vitality depends-a production of heat which will suffice to preserve his temperature at the same height, if, on quitting this atmosphere of 200°, he plunges into a snow-bath. For a short period a man can enter a furnace the floor of which is red-hot, the air being 350°, yet his own heat will remain 250° below this; and we cannot suppose that, in this brief period, he has lost enough heat by evaporation to prevent his own temperature rising. What, then, is the cause? We must confess inability to answer this question. For some 2 E |