Until about fifteen years ago the mammalian erythrocyte was considered to be a lifeless cell - virtually a parcel of hemoglobin - specialized for carrying oxygen from the lungs to the tissues. Lacking a nucleus and other common cell components, it is incapable of cell division and of carrying on the normal metabolic activity of ordinary tissue cells. It has long been known that the human red blood cell has a high content of potassium ions and a very low content of sodium ions despite the reverse of this ion distribution in the plasma, but earlier workers explained the situation by assuming that the cell membrane is impermeable to these ions.

The subject matter of this thesis is concerned mainly with two aspects of intestinal absorbtion. The first problem deals with the transport of amino acids and amino acid mixtures across the intestinal wall. The second is devoted to the study of transport of simple sugar mixtures. It was thought that the subjects could be more easily reviewed if the literature pertaining to the two problems was reviewed separately. The term intestinal absorbtion implies the passage of substances from the lumen into the blood stream in the intact animal, or from the mucosal solution into the outer serosal solution in in vitro experiments with intestinal segments.

Feldberg and Schilf (18) have given the name 'Gewebshormone' to pharmacologically active substances which are formed unspecifically by a number of organs and whose normal metabolic action seems to be a local one although they are capable of acting on organs some distance from their site of formation. Acetylcholine and histamine are two such substances.

The most obvious function of the blood clotting mechanism is to prevent the loss of blood from the vascular system, by the formation of a clot. It is easy to understand why excessive blood loss may occur after injury if the clotting process is impaired since the formation of the clot may be seriously retarded or even may fail to take place. It is much more difficult to understand why when the clotting mechanism is impaired spontaneous bleeding occurs even though no physical trauma has been imposed. [...]

The physiology and anatomy of the kidney are relatively well known due to the large number of investigations which have been carried out. One aspect of kidney function which has been neglected is that dealing with the excretion and reabsorption of biocolloids. In many disease conditions large quantities of a great variety of proteins may be excreted in the urine. The nature of the pathological changes involved in many of these diseases is not understood. One of the reasons for this lack of understanding is the absence of direct evidence concerning the normal processes involved.

The pioneer work in the field of in vivo studies of the corticosteroids present in adrenal venous blood vas carried out by Vogt (1943). She collected the adrenal venous blood from a heparinized dog and tested the blood plasma for cortical activity by biological aasay and found that adrenal glands produce large amounts of material with corticoid activity relative to the amount extractable from the tissue.

This series of experiments is based on work done by Dickens and Greville (1933) and Elliott am Henry (1946, 2). Dickens and Greville found that depriving brain slices of both substrate and oxygen for even short periods of time at 38° caused a marked decrease in the anaerobic glycolytic activity of the slices. Three minutes of the pretreatment caused a reduction of the glycolytic activity to 37%, while twenty minutes decreased it to 11-12%. Respiration, in the meanwhile, was only inhibited to about 50% even after forty minutes of anoxia in the absence of substrate at 38°.

The catabolism of steroid hormones and compounds, though not perhaps as worthy of attention as their anabolism or manner of biological synthesis, is a subject which has interested investigators for many years. It embraces the problem of the manner in which such a structure as the steroid nucleus might be completely dismembered in the living cell as well as the possibility that such a structure may undergo metabolic alterations rendering it more or less active with respect to a particular physiological property. [...]

In 1716 Montesquieu judged an essay contest on the subject "What is the Use of the Adrenal Glands". Some of the theories advanced were such as "to hold up the stomach, to dilute the urine, to collect the humidities which leak out of the great vessels surrounding them", and so on. Montesquieu decided none of the essays deserved a prize, awarded none.

One of the major steroids secreted by the rat adrenal has been shown to be the 2018 hemiketal of 18-nydroxy-11-desoxycorticosterone. This compound gives a positive Porter-Silber reaction but does not reduce tetrazolium. Its identification presents the first proof for the existence of a 21-hydroxylated steroid With a 20~18 hemiketal linkage as a natura11y occurring product. The compound appears to possess mineralocorticoid activity comparable to that of 11-desoxycorticosterone but no glucocorticoid activity. Its production by isolated rat adrenals is increased 10-fold by incubation with ACTH. Addition of 11-desoxycorticosterone produces a similar increase in the absence of ACTH.