pulsating, the chest heaving, the glands secreting or excreting, the digestive apparatus moving, and the brain thinking or receiving.

Let us, even in the prime of manhood, disturb this distribution of force ever so little, and straightway our life, which is the resultant of force, is disturbed. If we use the active force too long, we become exhausted, and call on the reserve; if we continue the process, the result is failure more or less perfect, sleep, and, in the end, the last long sleep; let us, instead of exhausting the force, cut it off at the sources where it is generated; let us remove the carbon or coal that should go in as fuel-food, and we create prostration, and in continuance a waning animal fire, sleep and death; or let us, instead of removing or withdrawing the supply of fuel, cut off the supply of air, as by immersion of the body in water, or by making it breathe a vapor that stops the combination of oxygen with carbon-such a vapor as chloroform-and again we produce at once prostration, sleep or death, according to the extent to which we have conducted the process. Lastly, if instead of using up unduly the active and reserve force, or instead of suppressing the evolution of force by the withdrawal of its sources, we expose the body to such an external temperature, that it is robbed of its heat faster than it can generate it if, that is to say, to supply the waste heat, we draw upon the active and reserve forces, we call forth immediately the same condition as followed from extreme over-exertion, or from suppression of the development of force: we call forth exhaustion and sleep, and, in extreme case, death.

We have had in our mind's eye, in the above description, a man in the prime of life, in the centre of growth, and decay. In regard to the force of animation in him, we may look at him now retrospectively and prospectively. In his past his has been a growing developing body, and in the course of development he has produced an excess of force commensurate with the demands of his growth; this enables him to bear a certain excess of fatigue and exposure, without exhaustion and even with ease, until he has reached his maximum. When he stops

in development, when he stands on a fair level with the external forces that are opposed to him, then his own force, for a short time balanced, soon sinks to be second in command. He feels cold more tenderly; if his rest be broken the demand for artificial heat is urgent; if he lose or miss food, he fails quickly; and returning to our facts, as to the influence of the external temperature on mortality, these are the reasons why a fall in the thermometer sweeps away our population according to age so ruthlessly and decisively.

If we analyze the facts further by the side of the diseases which kill, we find those diseases to be numerous in name, but all of one type; they are diseases which of themselves tend either to produce undue loss of force, or that tend to prevent the development of force as its origin. Disorders which are accompanied with exhaustive loss of fluids from the body, such as diabetes, dropsies, and hæmorrhages are of the first class; disorders in which due supply of air to the lungs is prevented, are of the second class, especially chronic bronchitis, which is in truth the assigned cause of two-thirds at least of the deaths that succeed immediately on the fall of the thermometer.

In what has been written above I have stated simply and in open terms the fact that the fall of temperature produces a specified series of results, by reducing the force of the living organism, and disposing it to die. We may from this point investigate the mode by which the effect is produced in the economy in a physiological point of view. How does the decline of temperature act? Is the process simple or compound?

The process is compound, and into it there enter three elements. In the first place, the body is robbed rapidly of its waste force, and the reserve and active elements of force are consequently called upon to the depression of the organism altogether.

This obtains because the medium surrounding the body, the air, unless it be artificially heated, receives from its contact with the body a larger proportion of heat than can be spared; and it might be possible to produce such an influence on the body by sudden extraction of its heat as to destroy it at once by the mere act. A man, as Met

calfe has remarked, a man half plunged into a bath of freezing mercury would die instantaneously, as from shock, by the immediate extraction of his heat. But in ordinary cases, and under ordinary circumstances, the mere rapid extraction of heat is not sufficient to account for all the mischief produced by a low temperature; for we take measures, by the use of non-conducting clothing, to counteract the mischief, and that, too, in a manner which proves pretty successful. We may, therefore, leave this element of extraction of heat as most important, but not all effective for evil.

The second element is the effect on the process of oxidation of blood. We all are aware that if a portion of dead animal or vegetable matter be placed at a low temperature, it keeps for a considerable time; and we have evidence of dead animals which, clothed in thick ribbed ice, have been retained free from putrefaction for centuries. Those ghastly bodies that occupy the dead-house of Mount St. Bernard on the Alps have lost water by evaporation, and are dried; but they are not putrid: they are preserved by cold, which means absence of heat. Hence we say that cold is an antiseptic as alcohol is, and chloroform, and ammonia, and creasote, and sulphurous acid, and other similar substances. Cold is an antiseptic, then, but why? Because it prevents, as do the bodies named a moment ago, the union of oxygen gas with combustible matter. The molecules of oxygen, in order that they shall combine, and in their combination evolve heat, require to be distributed, and are distributed by the force or motion known as heat: deprive them of this force, and they come into communion with themselves, are attracted to each other, and lose to the extent of this attraction their power of combining with the molecules of other bodies for which they have an affinity. In an analogous, but more obvious way, we may see the same effect of motion in the microscopic examination of blood. In the blood, while it is circulating briskly in its vessels, there are distributed through it, without contact with each other, millions of small round bodies, called blood corpuscles. In the circulation in the free channels of the body, the arteries and veins, it is motion that keeps these cor

puscles apart: we draw a drop of blood and let it come to rest on the microscope glass, and as the motion ceases, the separated corpuscles run together and adhere so firmly that we cannot separate them by any force less than disintegration. If we were to drive them in this state round the body, through the vessels, they would not combine readily with the tissues; they have, in fact, forfeited the condition necessary for combination. So with oxygen, when its invisible molecules are deprived of the force called heat, which is motion, they do not readily combine with new matter. But perfect combination of oxygen and carbon is essential to every act of life. In the constant clash and union of molecule of oxygen with molecule of carbon in the blood lies the mainspring of all animal motion; the motion of the heart itself is secondary to that. Destroy that union, however slightly, and the balance is lost, and the organic body is, in a plain word, ill.

Cold, or decreased temperature, below a given standard, which for sake of comparison we may take at a mean of 55° Fahrenheit, does destroy this combination of oxygen and carbon in blood. In the Lettsomian lectures of the Medical Society of London, delivered four years ago, I entered very fully into this subject, and illustrated points of it largely by experiment. Since then I have done more, and although I have not time here to state the details of these researches, I will epitomize the principal facts. I found then that, by exposing blood in chambers into which air could pass in and out, the blood could be oxidized at temperatures of 70° if the distribution of air and blood were effectually secured, and I also found a given standard of oxidation from a given temperature. Then I proceeded to test for combination at lower temperatures, and discovered a gradually decreasing scale until I arrived at 40° Fahr., when combination ceased altogether. Of course, my method was a very rude imitation of nature, but it was sufficient to show this fair and reliable result, that the oxidation of blood is arrested as the temperature of the oxygen decreases.

From this point I went to animal life itself. I exposed animals to pure cold

oxygen and to cold atmospheric air, and compared the results with other experiments in which animals of similar weight and kind were exposed to warm air and warm oxygen. The facts gleaned were most important, for they proved conclusively that the products of combustion, that is to say, the products resulting from the union of oxygen and carbon, were reduced in proportion as the temperature of the oxygen was reduced. In the course of this inquiry another singular and instructive fact was elicited. It has been long known that at ordinary temperature, say 60°, pure neutral oxygen does not support animal life so well as oxygen that is diluted with nitrogen. In the nitrogen the molecules of oxygen are more freely distributed under the influence of motion, that is the meaning of the observed fact. What, then, would be the respective influence of low and high temperatures on the respiration of pure oxygen? To settle this question, animals of the same size, kind, and weight were placed in equal measures of oxygen gas and common air at a temperature of 20° Fahr., and with the inevitable result that the animal in the pure oxygen ceased to respire one-third sooner than did the animal in common air. Carrying the inquiry further, I found that if the oxygen gas were warmed to 50° Fahr., the respiration was continued six times as long as in the previous experiment, while if the warming were carried to 70° it was sustained twentyfour times as long.

I need not carry this argument further; it is the easiest of the demonstrative facts of physiological science that the reduction of temperature lessens the combining power of oxygen for blood, and therewith causes a reduction of animal force, and a tendency to arrest of that force, death.

The third element in the action of cold is purely mechanical, and though in a sense secondary is of immense import. When any body, which is capable of expansion by heat, that is to say, by radiant motion of its own particles, is reduced in temperature, it loses volume, and contracts or shrinks. The animal body is no exception to this rule: a ring that will fit tightly on the warm finger will fall off the same finger after exposure to

cold. The whole of the soft parts shrink, and the vessels contract and empty themselves of their blood. Cold applied to the skin in an extreme degree blanches the skin, and renders it insensible and bloodless. If we prick it, it does not bleed, neither does it feel. In cases where the body altogether is exposed to extreme cold, this shrinking of the external parts is universal: the whole surface is pale and insensible; the blood in the small vessels superficially placed is forced inwards upon the heart and vessels of the interior organs; the brain is oppressed with blood; sleep, or coma, as it is technically called, follows, and at last life is suspended.

In exposure to the lowest wave of temperature in this country these extreme effects are not commonly developed: but minor effects are brought out which are most significant. In particular, the effect on the lungs is marked. The capillary vessels of the lungs, of that fine network which plays over the computed six hundred millions of air vesicles, undergo rapid contraction when the cold air enters the lungs; in proportion as such contraction is decisive, the blood that should be brought to the air vesicles is cut off, and the process of oxidation is thus mechanically as well as chemically suppressed. The same contraction is also exerted on the vessels of the skin, driving the blood into the interior and better protected organs. Hence the reason why on leaving a warm room to enter a cold frosty air there is an immediate action of the renal organs from pressure of blood on them, and not unfrequently a tendency to diarrhoea from temporary congestion of the digestive tract. Three factors then are at work whenever the low wave of temperature surrounds the animal organism: abstraction of heat from the body, and beyond what is natural; arrest of chemical action and of combustion; mechanical contraction of the vessels most exposed.

We cannot view the extent of these changes in the organic life, as induced by the low wave of heat, without seeing at once the sweep of mischief which exposure to the wave may effect. It exerts an influence on healthy life in the middle-aged man, and I know of no disease which it does not influence disas

trously. Is the man healthy, it tends to produce internal congestion; has he a weak point in the vascular system of his brain, it renders that point liable to pressure and rupture, with apoplexy as the sequence; is he suffering from bronchial disease, and obstruction already in his air passages, here is a means by which the evils are doubled; has he a feeble worn heart, it is unable to bear the pressure that is put upon it; has he partial obstruction of the kidney circulation, he is threatened with complete obstruction; is he indifferently fed, he is attacked with diarrhoea. It is from this extent of action that the mortality of all diseases runs up so fast, when the low wave of heat rolls over the population, taking, as we have seen, the feeblest first.

Another danger sometimes follows which is remote, but may be fatal, even to persons who are in health. It is one of the best known facts in science that when a part of the outer surface of the body has been exposed long to cold, the greatest risk is run in trying suddenly to warm it. The vessels become rapidly dilated, their coats give way, and extreme congestion follows. But what is true of the skin is true equally, and with more practical force, of the lungs. A man, a little below par, goes out when the wave of temperature is low, and feels oppressed, cold, weak, and miserable; the circulation through his lungs has been suppressed, and he is not oxidizing: he returns to a warm place, he rushes to the fire, breathes eagerly and long the heated air, and adds perchance to the warmth by taking a cup of hot drink; then he goes to bed, and wakes in a few hours with what is called pneumonia, or with bronchitis, or with both diseases. What has happened? The simple physical fact of reaction under too sudden an exposure to heat after exposure to cold. The capillaries of the lungs have become engorged, and the circulation static, so that there must be reaction of heat-inflammation-before recovery can occur. Nearly all bronchial affections are induced in this manner, not always or necessarily in the acute form, but more frequently by slow degrees, by repetition and repetition of the evil. Common colds are taken in this

same way: the exposed mucous surfaces of the nose and throat are subjected to a chill; then they are subjected to heat; then there is congestion, reaction of heat, pouring out of fluid matter, and all the other local phenomena.

The wave of low temperature rolling over a given population finds inevitably a certain number of persons of all ages and conditions on whom to exert its power. It catch s them too often when they least expect it. An aged man, with sluggish heart, go s to bed and reclines to sleep in a temperature say of 50° or 55°. In his sleep, were it quite uninfluenced from without, his heart and his breathing would naturally decline. Gradually, as the night advances, the low wave of heat steals over the sleepe, and the air he was breathing at 55° falls and falls to 40°, or it may be to 35° or 30°. may naturally follow less than a deeper sleep? Is it not natural that the sleep so profound shall stop the laboring heart? Certainly. The great narcotic never travels without fastening on some victims in this wise, removing them imperceptibly to themselves, into absolute rest, inertia, until life recommences out of death.

What

The study of the physiological influence of the wave of low heat, and of its relation to the wave of mortality, suggests two series of thoughts.

In the first place, it leads to ask, what are the best means of meeting the wave of low temperature? Necessarily all rules will be but imperfect, even though they be carried out perfectly; but there are a few which are simple, easy to be remembered, and of value.

(a.) Clothing is the first thing to attend to: to have the body, during variable weather, such as now obtains, well enveloped from head to foot in non-conducting woollen substance is essential: who neglects this precaution is guilty of a grievous error, and who helps the poor to clothe in flannel does more for them than can readily be conceived without careful attention to the subject we have discussed in all its details.

(b) In sitting-rooms or in bed-rooms it is equally essential to maintain an equable temperature; a fire in a bedroom is of first value at this season, and he who can invent an apparatus that

would sustain a small bed-room fire in an open grate all night, would be a true benefactor to his race, and soon a rich benefactor to boot. The fire sustains the external warmth, encourages ventilation, and gives health not less than comfort.

(c.) In going from a warm into a cold atmosphere, in breasting the wave of low temperature, no one can harm by starting forth thoroughly warm. A cup to keep out the cold, may be added also with advantage. But in returning from the cold into the warm, the act should always be accomplished gradually, and the cup to relieve the cold should be scrupulously avoided. This important rule may be readily borne in mind by connecting it with the recollection of the fact that the only safe mode of curing a frozen nose is to rub it with ice, and to restore the temperature as slowly as possible.

(d.). The wave of low temperature requires to be met by good, nutricious, warm food. Heat-forming foods, such as bread, sugar, butter, and potatoes, are, in moderation, of special use now. It would be against science and instinct alike to omit such foods when the body requires waste heat urgently and abundantly.

(e.) It is an entire mistake to suppose that the wave of cold is neutralized in any sense by the use of alcoholics. When a glass of hot brandy-and-water warms the cold man, the credit belongs to the hot water, and any discredit that may follow, to the brandy. So far from alcohol meeting the cold in action, it goes with it; alcohol stops oxidation, and acts as an antiseptic, so does cold; alcohol stops generation of heat, and therewith the motion of the heart in the living animal, because it stops oxidation, and cold does the self-same thing.

of the public towards the labors of medical men, who have to meet the effects of the low wave of heat. The public, looking on the doctor as a sort of mystic or high priest who ought to save, are too often dissatisfied with his work. Let the dissatisfied think of what is meant by saving, when there is a sudden fall in the thermometer. Let them recall that it is not bronchitis as a cause of death, nor apoplexy, nor heart disease, as such, that the doctor is asked to oppose, but an allpervading influence which overwhelms like the sea, and against which, in the mass, individual effort stands paralyzed and helpless. When the doctor is summoned, the mischief has at least commenced, and, it may be, is over, while treatment by mere medicines sinks in every case into secondary significance. Writing now to the public and not to the profession, I am of all things anxious to place this last part of my subject forcibly before them, that they may know how to be charitable to those who are called upon to minister to health, and may not laugh down those ministers who are candid enough to bow humbly before the great and inevitable truth, and who, professing no specific cure by nostrum, or symbol, try to lead towards recovery by teaching elementary principles, and by making the unlearned the participators in their own learning.

The title of this paper, suggested to me by the accomplished editor of the POPULAR SCIENCE REVIEW, would afford scope for a much more elaborate essay. Waves of high temperature have their specific influence also, encouraging some diseases and arresting others. I must not be tempted here to enter on this wider field, but catching the very cold inspiration of this season, must perforce, sternly as my mistress Nature herself, leave the good reader to console himself, as best he may, with that which is before him.

Leisure Hours. THE TUILERIES.

How magnificent is the aspect if we station ourselves by the Arc de la Triomphe, and look down the long avenue of the Champs Elysées! Beyond the Obelisk and statuary and fountains of