Consumption of Smoke. 535 clear as that of the great city of New York in America, where only stone coal is burned, or of St. Petersburg, Berlin, and the other European cities, where winter heating is obtained altogether through close stoves. Various furnaces have been contrived for the avoidance of smoke and the perfect combustion of fuel, and several Acts of Parliament have been passed to compel the use of furnaces which shall consume their own smoke, but in spite of these enactments, the nuisance to the metropolis is maintained by the wasteful use of coal in private houses. “Man, by the command which he has acquired over heat and fire, can produce artificially the climate which suits his constitution in any part of the globe." 755. It is a remarkable fact in nature that living animal bodies have the property of maintaining in themselves a certain nearly uniform temperature, whether surrounded by bodies that are hotter or colder than themselves. Persons passing the winter near the north pole, where they are breathing air cold enough to freeze mercury, still have in them their natural warmth of 98° Fahrenheit; and the inhabitants of India, where the thermometer sometimes stands at 115° in the shade, have their blood only 98° warm. 756. In the valley of the Indus and in Upper Egypt, the thermometer has been seen standing at 138° to 140°. The effect of breathing such extremely heated air is to produce copious perspiration. The evaporation of this from the skin is a cooling process, and tends to keep down a high temperature within the body. The Turkish bath furnishes another proof of this wonderful power in the living body to resist a high external heat. In some cases the temperature to which a human being has been exposed in this hot-air bath has been as high as 170°. As a rule this temperature is only gradually reached. The effect of breathing air so heated, is to produce a feeling of suffocation, dizziness, and a most rapid circulation. As this is the degree of heat at which the albuminous principle of the blood coagulates, nothing but a rapid circulation combined with vital force, can prevent the liquid blood from becoming consolidated in the vessels. 757. In the mammalia generally the temperature of the body averages 101°; in birds it is as high as 107°, and sometimes reaches 111°. This very high temperature is observed chiefly in the smaller species. These temperatures are maintained, as in the human body, in spite 536 Temperature of the Bodies of Animals. of constant changes in the surrounding atmosphere, and their maintenance is, as we shall see presently, absolutely necessary to life, and to the due performance of those functions of the body on which life depends. Perhaps we can point to no greater contrast between living and dead matter, than is shown by the resistance of a living body to the equalization of temperature. On what does this power of resistance depend? Assuredly not on the physical and chemical properties of the solids and fluids of the body, for so soon as death takes place the body of an animal begins to cool, and the cooling goes on as with inert or inorganic matter, until the temperature is the same as that of surrounding objects. We speak of warm-blooded and cold-blooded animals, reptiles being placed generally in the latter class. John Hunter proved that this does not imply an absolutely higher or lower temperature, but simply a temperature which is liable to change with the atmosphere. Reptiles have generally a temperature a few degrees higher than the medium in which they live, and they may feel hot or cold according to the changes in the external atmosphere. In order to maintain a uniform temperature in the living body, heat must be produced in sufficient quantity to compensate for that which is lost by radiation, by convection in a moving atmosphere, and by evaporation of fluids from the exposed surfaces.* 758. Every kind of animal has a temperature proper to it, and in the diversity of animals, are found creatures fitted to live in all parts of the earth; what is wanting in internal bodily constitution being found in the admirably adapted covering which protects them-a covering which is a product of their food, and grows from their bodies in the form of fur or feather, in the exact degree required, and even so as in the same animal to vary with climate and season. No such covering is possessed by man ; but his reason, by which he subjects all nature to his use, enables him to clothe himself as befits the part of the globe in which he chooses to dwell. 759. On this subject Dr. Kirkes remarks that the loss of heat sustained by animals, differs greatly according to circumstances, and there is a similar difference in the degrees of power which they possess * Dogs, it is well known, when much heated by exercise, or by the weather, do not perspire through their skins, but throw out by their long humid tongues, a large evaporating surface by which their high temperature is reduced. Temperatures borne by Animals. 537 of adapting themselves to such differences. Some live best in cold regions, where they produce abundant heat for radiation, and cannot endure the heat of warm climates, where the heat which they habitually produce would probably be excessive, and by its continual though perhaps small excess, would generate disease: others, naturally inhabiting warm climates, die if removed to cold ones, as if because their power of producing heat, were not sufficient to compensate for the larger abstractions of it by radiation. Man, with the aid of intellect for the provision of artificial clothing, and with command over food, is in these respects superior to all other creatures, possessing the greatest power of adaptation to external temperature, and being capable of enduring extreme degrees of heat as well as of cold without injury to health. His power of adaptation is sufficient for the maintenance of a uniform temperature over a range of 226° of Fahrenheit's thermometer,* a power which is shared by a few domestic animals. 760. The power in men and animals of preserving their peculiar temperature has its limits. Intense cold coming suddenly upon a man who has not sufficient protection, first causes a sensation of pain, and then brings on an almost irresistible sleepiness, which, if indulged, proves fatal. Sir Joseph Banks, in one of his voyages, having gone on shore near the cold Cape Horn, and being fatigued, was so overcome by the feeling mentioned, that he entreated his companions to let him sleep, if but for a few minutes. His request, if granted, might have allowed to come upon him the sleep of death, as befell so many of the hostile army retreating from Russia through the snows of 1812, when in one night the thermometer fell to 19° below zero, and, according to the bulletin, 30,000 horses perished, besides men. Cold in less severe degrees, acting through longer periods on persons imperfectly protected, induces a variety of diseases, which destroy life more slowly,—as many of the winter diseases of England. 761. The human race, when not possessing certain arts of civilization, naturally seek a warm climate, such as exists over vast regions on both sides of the equator. There the sun's influence is strong and uniform, producing a rich and warm garden, in which human beings, however ignorant of the world around them, would have all their necessities at once supplied. The ripe fruit is there always * See table, p. 506, in which the extreme of cold observed by Erman in Siberia was -72°, and the maximum of heat in West Indian steam. ships 154°. 538 Influence of Disease on Animal Heat. hanging from the branches; of clothing there is required only what moral feelings may dictate, or what may be supposed to add grace to the form; and as shelter from the weather, a few broad leaves spread on connected reeds, complete the tropical hut. The human family, in multiplying and spreading in all directions from such a centre, would find, to the east and west, only the lengthened paradise, with slightly varying features of beauty; but to the north and south the changes of season, which cause the bee of high latitudes to lay up its winter store of honey, and send migrating birds from country to country to find the required warmth and food, would also rouse man's energies to protect himself. His faculties of foresight and contrivance would come into play, and through these and his power to produce at will and to control the wonder-working principle of heat, he is enabled to exist in all climates, from the equator almost to the poles. Influence of disease on Animal Heat. 762. Although the average temperature of the body in a state of health is from 98° to 100°, it is liable to be increased or diminished by disease, and the clinical thermometer is now much used by physicians as an indication of recovery or approaching death. The temperature of the body is usually determined by placing the thermometer under the tongue or in the armpit. Clinical thermonieters, which are specially constructed for these observations, are of extreme delicacy, and their accuracy is generally determined by comparison with a standard kept at the Kew Observatory.* The delicate thread of mercury by which the measurements are made is less than the 1th of an inch in diameter. In one of these instruments, which the writer examined, there were five divisions to a degree, and three degrees corresponded to half an inch of the tube. The temperature, therefore, admits of measurement to small fractions of a degree. The cylindrical portion of the tube containing the mercury (fig. 180), is about half an inch in length, is thin, and presents a large surface, so that it may be quickly affected. The graduation begins at 90°, and does not extend beyond 110°, this being the ordinary scale for the extremes of temperature usually observed. In children the temperature is often as high as 102°. Of the external parts, the temper *This is the rule regarding the thermometers made by Pillischer of Bond Street. Each instrument is accompanied by a special certificate setting forth any differences. High and Low Temperatures. 539 ature is observed to become lower, the further they are from the centre of the body. Thus on the thigh the temperature will be 94°, and on the sole of the foot 90° (Davy). In scarlet fever and typhus the temperature is observed to rise to 107°, and in children affected with these diseases, the skin has been observed to have a temperature of 108.5°. In a girl of sixteen, suffering from inflammation of the lungs, the temperature gradually rose up to the fifth day, when it stood at 107.5°. On the sixth day it fell to 104°. This is considered to be the average temperature of fever-heat. In a youth of twenty, also attacked with the same disease, it was noticed that in thirty-four-hours his temperature had risen to 110°. On the next morning it had fallen to 99o. It has been stated that 110° is the extreme limit to which the temperature of the human body could be raised without a fatal termination, and it is highly probable that this statement is correct, assuming that it is maintained for a certain time. In a fatal form of rheumatic fever it has been observed that if the temperature quickly reaches 108° or 109°, the patient dies. 763. Delaroche found that animals died when kept in air heated gradually to 13° above their natural standard. Rabbits and birds have also died when, from exposure to great external heat, their temperature has risen 9° above the natural standard. In a fatal case of injury to the spine the temperature rapidly rose before death to 1112°. In another instance in which death took place seventeen hours after the injury, the temperature rose to 110°. -110 5 -100 5 ៥០ Fig. 180. Dr. Wilks states that a temperature of 109° or 110° is incompatible with life, and thus we have at last found a clue to the cause of death in sunstroke and in some remarkable disorders. The former, which is more correctly called heatstroke, may occur in a hot climate in the night as well as the day, and is due to the sudden rising of the temperature of the body from the external heat, and inability to throw off the retained heat from some peculiar state of the atmosphere. As a summary it may be said, if the temperature of the body rises 10° or 12° above the normal state, the blood and muscles undergo a change, and life must cease. The administration of various drugs has been found to influence |