In 1855 Addison described a group of symptoms, among which was a weak thready pulse, which were associated with bilateral descruction of the adrenal glands (1, 2). These findings were the first indication that the adrenal was important in the regulation of blood pressure. [...]

Although he apparently never used it himself, Fick in 1870 elaborated the well known principle, bearing his name, for measuring cardiac output. He expressed it in the same form as it is presently used, i.e. that if one knows the amount of oxygen taken up by the lungs per unit time (or the amount of carbon dioxide eliminated also per unit time) and the difference in concentrations of oxygen (or carbon dioxide) between the arterial and the venous blood, then one can calculate the amount of blood flowing through the lung during that time. [...]

The influence of stress and adrenalin, and later, of adrenal steroids on thyroid function in man and in experimental animals has interested investigators for many years. This interest arises from the requirement to elucidate and clarify physiological functions of the thyroid gland, the regulation of these functions, and the role of the thyroid in the homeostasis of the body and its reactions to stress. In addition the possible role of stress in the etiology and pathogenesis of diseases of the thyroid gland has been suspected for many years (1) and is currently the subject of several experiments.

In the past decade pulmonary function tests have assumed an increasingly important and useful role in the field of diagnostic medicine. Many such tests have been devised, but if we consider the lung as ultimately concerned with the exchange of gas between atmosphere and blood, the measurement which perhaps best estimates this process is the pulmonary diffusing capacity. Although the test was conceived early in the century, in the past few years there has been a sudden spurt in its development. [...]

Clinically, relatively large changes in the body water of animals are made apparent by the signs characteristic or dehydration and edema. However the measurement of the distribution of the water among the various body fluid compartments in vivo is a largely unsolved problem. [...]

The protean findings on patients with adrenocortical tumors and the fact that the adrenal cortex is requisite to life has long been established. Tilesius, in 1803, described obesity, precocious breast development and hirsutism in a girl of four, found to have a tumor of the adrenal cortex. [...]

Research in the field of pulmonary function has been moving forward at an increasing pace in the past few years. The major stimulus intensifying this work came from Great Britain where the morbidity and mortality of chronic bronchitis has become the principal health problem. There are very few comprehensive studies dealing with the changes of pulmonary function with increasing age. A majority of the work available for review has involved only one or two specific tests of lung function, or has covered too wide a range of ages, thus making valid comparisons difficult.

The following work was originally undertaken in December 1951, with the hope of studying the ACTH-like activity of human blood in different physiological and pathological conditions. The acid acetone extraction of blood and the adrenal ascorbic acid depletion in hypophysectomized rats (Sayers' test) were selected as the most suitable means of approach at this time, without realizing the difficulties attendant upon the setting up of this test in the absence of extra technical assistance.

The study of the mineralocorticoid aspect of adrenal cortical activity has been accelerated in recent years by the isolation of aldosterone (1-5). That this aspect of adrenal cortical activity may be altered independently of its other aspects has been well demonstrated by the numerous published studies relating to the sodium-retaining factor recovered from the urine in various disease states (6-15).

Rhythmic 24 hour variation of physiological function, in common with many other poorly understood problems, is subject to confusion in terminology. In this thesis the word "diurnal" will be used to describe events occurring during the course of a 24 hour period, not solely those occurring during the daytime. This is a concession to common usage in this field. "Nocturnal", on the other hand, will refer to events during the night; its equivalent adjective during the day will be "daytime", "matutinal", or "forenoon" and "afternoon”.