The Importance Of Body Temperature

Article #1: The Importance Of Body Temperature by Dr. Herbert M. Shelton

Warmth is one of the necessities of life. Vital activities are possible only between certain narrowly defined limits of temperature. Cold inhibits and excessive heat suspends them. Body heat is energy. It is employed not just in resisting cold, but also in accelerating cellular activities. Temperature, within certain narrow limits, is so absolutely essential to life that all functions are excited by any attempt at its variation. Animals are roughly divided into two major classes: warm-blooded and cold-blooded. This is according to whether they have means of producing and maintaining their own temperature or are dependent upon the surrounding medium (water or air) to provide it.

The invertebrates, although they breathe oxygen and cir­culate fluids throughout their bodies, have no red blood corpuscles and are cold-blooded animals. Fishes and reptiles, vertebrates with red blood cells, are also called cold-blooded animals, although they are able to maintain an internal temperature above that of the surrounding water or air. Invertebrates have no heat of their own, but receive their temperature from the surrounding media and adapt to it. Except for fishes and reptiles, whose heat-producing and heat-regulating powers are very limited, we may say that all vertebrates are warm-blooded, having red corpuscles, while the reverse is true of the invertebrates which have no red corpuscles.

It may be suggested that since animals can live without red corpuscles and exist without internal heat, the primary office of respiration is more universal than to provide for the production of animal heat. Using a popular phrase in biology, heat production is only a “secondary adaptation.”

If we look at a large number of lower animals, we find them to be small and living in water. This medium directly and powerfully reduces them to its own temperature, and they are surrounded and permeated with water. In the radiata water actually mingles in large quantities with their digested food, so that they must of necessity remain at or very near water temperature. Even if they possessed sources of heat within themselves, it becomes evident that heat production cannot be the great end of respiration in these animals. Its primary function must be something very different from this.

If we take a second look at these animals, we discover that large numbers of them, especially those that live in fresh water, vary in temperature with the medium in which they live. Often they vary to a great extent, being some­times near the freezing point and at other times fifty to one hundred degrees above it. Although a particular tempera­ture may be best for each of them, still, many of them can live an active life in temperatures seventy, sixty, fifty and even forty degrees less. It is obvious that the small extent they could raise the temperature of their bodies above that of the water, when it is forty or fifty degrees, would be of no great importance. In their case at least, there must be some more important end for respiration than production of heat.

Heat supplies a necessary condition of vital activity. The activities of cold-blooded animals rise and fall as the temperature goes up or down. The higher the temperature, providing it does not go so high so as to destroy life, the greater the activity. If it becomes very cold, they suspend activity. It is not in inorganic chemistry alone that heat promotes the energy and intensity of action. In “vital chemistry,” that is, in living functions, the same phe­nomenon is observed. An elevation of temperature ac­celerates all vital functions, both in the cold-blooded and in the warm-blooded animals. A similar thing is seen in plants.

Acceleration of activity increases with the rise in temper­ature until the temperature reaches a certain variable opti­mum, after which any added increase in temperature reduces activity. The rate of activity for some of the lower forms may become so great as the temperature rises that they “live too fast” and wear themselves out.

When temperature is lowered, vital activities are low­ered. In the cold-blooded animals, some of which may be frozen for long periods and then revived, all activity ceases after the temperature is reduced below a certain variable minimum. Most of the warm-blooded animals die when frozen, their vital activities ceasing before they reach the state of freezing.

Higher animals are not so dependent upon the surround­ing temperature. They are not only equipped with internal sources of heat and mechanisms to control its production and radiation, but they also in most instances have outer coats of hair, feathers or wool to protect them from the cold. They possess means of lowering heat production and increasing heat radiation if the external temperature or their own internal heat due to activity is increased. (By the operation of the same internal heat-regulating mechanism they produce fever when needed.)

Thus, while the very form and habits of the lower orders of life are determined by external surroundings, the forms and habits of life of the higher animals are very largely determined by powers within them. These often prevail over powerful antagonistic forces without.

The lower animals are more or less slaves to the external world; the higher animals make the external world serve them. It should be noted that this independence of the higher animals, this internal energy, is in great measure due to a capacity for maintaining their normal temperatures amid the changes in that of the surrounding water and air.

The uniform temperatures maintained by higher animals promote and secure a constancy, precision and energy in the nutrition of their tissues, and in the vital functions that supply the animal with resources to carry on active life in the face of opposing influences in the world.

A brief glance at the method of maintaining body temperature may be helpful. In the chapter on respiration we learned of the office of oxidation in the production of heat. It is necessary that we understand that the body is capable of both increasing and decreasing its rate of heat production as the external temperature falls or rises. These processes are rigidly controlled by the nervous system and fail only in greatly enervated and diseased organisms.

But the body also increases and decreases the radiation of heat from the body as need arises. While oxidation warms the body, evaporation (as in sweating) cools it. These physiological processes are carried on in relation to vital wants. The human body, to narrow our considera­tions at this point, is based upon a system of self-regulation and equipoise, and its temperature relations are beautifully provided for. In a cool atmosphere less heat is lost by evaporation and more produced within the body, while a reverse process is seen in a warm temperature.

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In all changes of temperature outside the body, some compensatory effort is required. But if our other relations are correct, the internal heat-regulating capacity of the body will be efficient. The maintenance of the heat-making mechanism of the body is an indispensable condition of health. Feeble and sick individuals who find it difficult or impossible to maintain normal temperature in a cold climate need to be kept warm. Chilling inhibits all func­tions of life and reduces their already greatly reduced stock of energy. The escape to a warm climate is no mere luxury for such persons. Warmth of some degree is certainly a normal requisite of life. But experience and experiment have shown that when the temperature of the surroundings is out of all proportion to the needs of the body and to its capacity to adjust itself, the body must and does suffer. There is not only discomfort, which normally causes us to seek relief from extremes of heat or cold, but there is some expenditure of energy in resisting extreme temperature.

In lands where fogs, frost and darkness cramp the ener­gies of man, as well as in regions where excessive and long-continued heat depresses his vital activities, life is handi­capped. By means of clothing, housing and artificial heat­ing arrangements, we are able to live in cold climates. By means of cooling systems and a reduction of clothing, we live more comfortably in hot regions and seasons. But none of these arrangements are ideal. A warm climate serves man best; first-class habits of living enable him to live better in whatever climate he resides.

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