August Krogh

Osmotic Regulation in Aquatic Animals

August Krogh, 242 pp.,

The rate of diffusion of gases through animal tissues, with some remarks on the coefficient of invasion

1.75, Dover, New York, 1966. Material in this book is presented in a systematic fashion with separate chapters devoted to osmotic regulation in each of the major phyla of invertebrates and vertebrates, and one chapter is devoted to osmotic problems encountered by eggs and embryos of aquatic animals. The scientific name of each animal discussed is given and at least some mention is made of osmoregulation in several hundred genera with some discussed at length. A section perhaps as useful to the teacher of zoology or comparative physiology as any part of the book is the final short chapter dealing with methods. Among others, simple techniques for determination of osmotic concentration and of volume changes are included. The methods presented are ones feasible for use in student laboratories and do not require elaborate equipment. An extensive list of references concludes the volume but, by the authors own admission, it is not a comprehensive list. Since the book was first published in 1939 and has not been altered, no recent references are included. Information is presented in a fashion perhaps too sophisticated to make the book of great use to the beginning science student since the author presupposes some knowledge of biology and chemistry on the part of his reader. However, such an accumulation of material concerning osmoregulation as is presented by Professor Krogh would be difficult, if not impossible to find in any other single volume. For this reason, this book could well occupy a place in the library of any biologist. Barbara Shirley Department of Life Sciences University of Tulsa Tulsa, Oklahoma

The supply of oxygen to the tissues and the regulation of the capillary circulation

THE rate at which gases and especially oxygen will diffuse through tissues has, so far as I am aware, never been systematically investigated and practicallv never been investigated at all, though a knowledge of the gas diffusion is obviously essential for the solution of one of the problems of the physiology of to-day: the supply of oxygen to the cells. The brilliant work of B a rcroft and his collaborators has made it comparatively easy to obtain a quantitative idea of the average oxygen tension in the capillaries and has furnished many of the necessary data concerning the call for oxygen of the tissues, but in order to make out how this call can be met it is necessary (1) to measure and calculate the average distances which the oxygen molecules have to travel from the capillaries until they enter into chemical combination, and (2) to know the rates at which they travel, that is the diffusion coefficients for oxygen in the different tissues. The present paper is intended to supply the second of these desiderata for certain tissues. The diffusion of gases through animal tissues must take place in essentiallv the same way as their diffusion through fluids or colloidal membranes. The gases are dissolved in the tissue fluids and diffuse in a liquid state. The laws governing the diffusion of gases through water and watery solutions have been worked out by Exner(i), who found that the rates of diffusion for different gases in the same fluid are proportional to the absorption coefficients of the gases in the fluid and inversely proportional to the square roots of their molecular weights. Exner could onlv measure relative diffusion rates for different gases. Stefan(2) measured directly the rate of diffusion of carbon dioxide. Hufn er (3) devised a method for measuring directly the diffusion rates

Studies on the capillariometer mechanism

IN a previous paper I have deduced from the distribution and number of capillaries(l), the diffusion rate for oxygen(2) and the oxygen consumption of the various tissues that the oxygen pressure everywhere in the organism and especially in the muscles must be practically equal to that of the capillary blood, the pressure head necessary to maintain the oxygen supply being extremely low. This deduction does not agree with the results of certain earlier investigations of the oxygen pressure in the tissues of warm blooded animals, and it will be necessary therefore to try and clear up the discrepancies. We can leave out of account as untrustworthy the determinations based upon the method of E hr 1 i c h (3), as the power of tissues to reduce certain stains has very little to do with the presence or absence of free molecular oxygen. As pointed out in my monograph on the respiratory exchange (4) (p. 77) the tension determinations on secretions (Strass burg(5), Fredericq (6)), which have usually shown that free oxygen is practically absent, are likewise untrustworthy, because oxygen is used up at a comparatively rapid rate (PflIUger(7), Krogh(4)) in the fluids in question, and there is definite evidence that in certain secretions (urine, K ro gh (4)) the 02 pressure is normally not much, if at all, lower than in the venous blood. The experiments of T ob i e s e n (8) show that any gas mixture (or pure gas) introduced into the pleural cavity of man will finally get an oxygen tension of 3-4 p.c., and similar results have been found for the abdominal cavity of animals. Though it must be admitted that the introduction of air into the body may possibly influence the circulation in the adjoining tissues and increase their oxygen supply,

The number and distribution of capillaries in muscles with calculations of the oxygen pressure head necessary for supplying the tissue

THE series of papers of which the present one is the first has as its object a revision of current conceptions concerning vasomotor regulation and the mechanism of vasomotor changes. The prevalent line of thought and argument identifies vasomotor changes with arteriomotor. It considers the smaller arteries and arterioles as being generally capable of contraction and dilatation and assumes openly or tacitly that all other c.hanges in calibre taking place in peripheral vessels and especially the state of filling of the capillary system follow as physical consequences from the general blood-pressure and the state of contraction of the arteries and arterioles. In my paper on the supply of oxygen to the tissues(1) I have given several reasons against this view and quoted researches by other workers showing like my own that the calibre of capillaries is not simply a function of the pressure of the blood coming from the arterioles, but that the capillaries show independent reactions and may dilate and contract individually and independently of the blood-pressure within their walls. A special reference should here be made to the important work of Dale and Richards(2) and of Dale and Laidlaw(3) published after my paper had been written. The researches of Dale and Richards show conclusively that histamine and minimal doses of adrenaline have a dilator effect on the capillaries of certain animals which is independent of the nerve supply, while the effect of these substances upon arteries is that of constriction. Dale and L.aidlaw have shown further that large doses of histamine produce an excessive dilatation of the capillary vessels followed by transudation of plasma. In the paper mentioned (1) my chief object was the study of the supply of oxygen to the fibres of striated muscles, and the vasomotor problems involved could only be treated briefly. The experiments then made could only show the inadequacy of the orthodox conception, but