The Interaction of Body Temperature and Acid-Base Balance in Ectothermic Vertebrates

Sir Joseph Barcroft began his 1934 volume Features in Architecture 0/ Physiologi­ cal Function (9) with two essays illustrating Claude Bernard's dictum: La fixite du milieu interieur est la condition de la vie libre, first essay noted sensitivity of cellular activities to hydrogen ion concentrations, observing due to life processes there is . . . every opportunity for hydrogen ion concentration of internal environment to be inconstant; yet it remains remarkably constant within narrow limits in man and other mammals. Concerning application of this principle to lower , Barcroft stated: The extreme limits of hydrogen ion concentrations in blood of sub-mammalian forms are given differently by differ­ ent authors and are quite obscure. In his second essay Barcroft dealt with tempera­ ture, noting the temperature of man is approximately constant, and mused on remarkable proposition that at any one temperature all reactions of body should progress at velocities suitable to one another. He went on to ask: How does body of animal of variable temperature so control its reactions as to keep them in step over a great range of temperature? It has taken many decades since Barcroft wrote to perceive that, for all verte­ brates, a direct relationship exists between subjects dealt with in these essays, i.e, between regulated hydrogen ion activity and temperature, a relationship only clarified through study of many animals of variable temperature. It is more accurate, as we see later, to substitute for hydrogen ion activity (or pH) happy phrase of Henderson's (42), acid-base balance, which is preserved upon chang­ ·ing body temperature. More recently it has been recognized particular balance achieved is not constancy of blood pH Barcroft sought, but is rather