Claude Bernard "The constancy of the internal environment is the condition for a free and independent life.”

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Claude Bernard was a French Physiologist who was best known for his works and discoveries during his lifetime in the field of digestive processes, the liver and the regulation of the supply of the blood though the vasomotor nerves. The most renowned and important discovery of Bernard was related to use of the secretions of the pancreatic tissues to break down the molecules of fat into smaller particles so as to aid the digestion process and the other specific discovery was that the principle process of digestion does not takes place in the stomach rather it takes place in the small intestine. His next discovery unveiled the ability of the liver to split the reserves of the glycogen energy into sugar particles so as to use them as a quick source of energy for the body and to maintain the levels of the sugar in the body. Finally, Bernard discovered the control of the vasomotor nerves on the blood vessels and how it responds to the changes in the temperatures while operating in an environment. With this the Bernard was able to advance his work on blood vessels and tried to understand the ability of the body to constantly maintain the internal temperature. This led him to formulate the ideas in relation to the constancy of the internal environment of the body. In 19th century his concept of constancy of internal environment (milieu interieur) was officially presented.

The constancy of the Internal Environment

The metabolic theory of the cell, proposed by Theodor Schwann was generally ignored by the French scientists. This theory laid emphasis over the importance of the “Nutritive medium bathing the cell”. Bernard views the application of this concept in the fundamental problem of physiology, the existence of the relationship between the cells and their corresponding environment. Claude Bernard was the first scientist who proposed that the complex animals operate in two environments, namely, the external environment in which the organisms are living and the internal environment where the cells are functioning. This was the basis of the well known theory proposed by Claude Bernard in the 19th century: “The constancy of the internal environment is the condition for a free and independent life.”

The concept of the constancy of the internal environment was contributed by Claude Bernard which was the first systematic analysis of the functioning of an organism. Bernard was an exceptional experimentalist. Claude Bernard addressed a problem in the 19th century in which he reported that the organic molecules had been created by the chemists. It was a major development for the people because they knew that there exist only three classes of compounds that are completely separated from each other, namely, vegetable, mineral and animal. In 1784, Lavoisier showed that all the compounds that are derived from the sources of vegetable and animal always contain carbon and hydrogen, and most of the times it also contains nitrogen and phosphorus. This work bridged the boundary of the vegetable–animal chemical. However, the boundary between the non-living and living remained intact.

In 1815, Berzelius proposed that the organic compounds were produced by laws that were different from that of the inorganic compounds, that a specific vital force is unable to operate outside the living systems. There were several other discoveries which concluded the life can reduce itself to physics and chemistry. Such type of challenge was faced by Claude Bernard.

Bernard answered precisely that the living organisms cannot be characterized by the vitalism or chemical reductions. He further reported that though the individual organic compounds are well defined in their properties, but they cannot be considered as active elements in physiological phenomena. They should only be considered as passive elements in the organism. The reason behind this statement was explained as, “The living organism does not really exist in the milieu ext´erieur but in the liquid milieu interior.... A complex organism should be looked upon as an assemblage of simple organisms.... That lives in the liquid milieu interior.”

Claude Bernard also believed that there is no distinction between the principles of the biological science and the physico-chemical science. The control of the milieu Int´erieur means that the individual molecules do not do anything different from that of the non living systems, but rather they behave in a controlled way which helps in maintaining the constancy of the internal environment.

Biological functionality is multilevel

Claude Bernard’s idea of the constancy of the internal environment suggests that the biological functionality is multilevel. It is a true statement because it is a well known fact that the functionality in the organisms is attributable as a whole and all the levels are controlled by it. This statement was identified by Bernard and hence it would not be wrong to say that Bernard was the first systems biologist. In the middle of the nineteenth century, the principle of control of the internal environment was formulated by him. This principle is now recognized as the homeostatic basis of modern physiological science. The term Homeostasis was coined by Walter Cannon who also proposed different propositions so as to explain the features of the homeostasis.

  1. Homeostasis is manifested usually by the internal constancy like body temperature, acid based balance and concentration of glucose.
  2. The factors that resist the change are induced by the tendency towards the change.
  3. The internal constancy is cooperatively maintained simultaneously or successively by the mechanism of the regulation act of physiology.

Bernard explained that a living body is relatively independent of the surrounding environment. However, the fact behind this independence is that the tissues in the living body are protected by a veritable internal environment that is composed of the fluids that are circulating in the body.

Initially the internal environment from the perspective of Bernard was simply the blood that is circulating in the body. But at such stage, Bernard was able to understand that the temperature of the circulating blood is regulated actively and its constancy is specifically critical in the higher animals. Higher animals were not completely independent of the external environment, but they are in intimate and close relation to it, so that the exact and continuous compensatory adjustments help them to achieve the equilibrium.

The works and the discoveries provided by Bernard marked the beginning of a new era where the animated anatomy was superseded by biochemistry as a key to the methodology of the physiological research. The physiology in the modern era is considered as a parent science of the cell physiology, biochemistry and endocrinology that found its roots in the field of anatomy and medicine.

With the help of the approaches formulated by Bernard, several vital phenomena were discovered by different physiologists in regard of the processes of self regulations. “The concept of the constancy of the internal environment” was established by Lawrence J. Henderson as the key to the physiology.

On the basis of the research reflected during the lifetime of Claude Bernard, concluded that there is “only one simple way to live, the same physiology of all the living things”.