Naked Science Forum
On the Lighter Side => Famous Scientists, Doctors and Inventors => Topic started by: Andrew K Fletcher on 13/05/2005 21:13:03
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In Memory of
Professor Harold T. Hammel, Ph.D.
March 4, 2005
Harold Ted Hammel, Ph.D. and Professor Emeritus, died on February 24, 2005 in his 84th year of life. After his academic education in Physics and Zoology/Zoophysiology, the stations of his career in physiology were the University of Pennsylvania, Philadelphia, the John B. Pierce Foundation Laboratory at New Haven, an institution associated with Yale University, and – until his retirement – the Physiological Research Laboratory of the Scripps Institution at La Jolla, where he also served as Professor of Physiology of the University of California, San Diego. After his retirement he remained active as an Adjunct Professor of the Human Biology Department of the University of Indiana at Bloomington. The field of research to which H.T. Hammel made his first internationally recognized contributions, was adaptation of humans to extreme climatic conditions. His field studies done in co-operation with the late P.F. Scholander on indigenous populations (Kalahari Bushmen, Australian Aborigines and Alacaluf Indians at Tierra del Fuego) will forever maintain their value as unique documents of the strategies of adaptation to cold developed by these populations living under very different conditions of cold exposure and food supply. H.T. Hammel has become world-famous by his work on the hypothalamus of homeotherms for which he was the first to quantify its thermosensory function as input signal into the natural feedback system of thermoregulation. His results stimulated laboratories all over the world to proceed on the basis of his discoveries and, in particular, they served as the touchstone for the experimental approach to deep-body thermosensitivity in general, leading ultimately to the current concept of thermoregulation as a multiple-input/multiple-effector feedback system. Cooperation of H.T. Hammel with the Department of Physiology, Max-Planck-Institute for Physiological and Clinical Research (now Heart and Lung Research), W.G. Kerckhoff-Institute, Bad Nauheim, Germany, had been initiated as early as 1963 on the occasion of field studies on human cold tolerance in the Highlands of Southern Norway (Hardanger-Vidda). It culminated first in common work on thermo- and osmoregulation of the Adelie Penguin during an Expedition to McMurdo, Antarctica in 1975. Further joint research was put on an official basis, when H.T. Hammel was elected in 1978 as External Scientific Member of the Max-Planck-Institute at Bad Nauheim. This appointment not only has been held by him in great esteem, but it started the period of his continuing collaboration with researchers of this institute’s Physiology Department in the fields of thermo-and osmoregulation. During 12 successive years, until his retirement, H.T. Hammel spent between 3 and 6 months every year at Bad Nauheim, often accompanied by his wife Dorothy, making important contributions to the analysis of salt and fluid balance, one of the department’s main fields of research. Above all, however, water as the medium of life has remained in the focus of H.T. Hammel’s interest from the start to the end of his life as a scientist. In animals and plants he has continuously studied and analyzed water transport induced by evaporation and osmosis. Based on seminal experiments and on decades of thinking he developed his original hypothesis of altered water tension underlying the phenomena of water transport and he has continued to refine the presentation of his concept. The controversy with proponents of the classical theory of the colligative properties of water, in which he slowly but continuously has gained ground, had become his “elixir of life” keeping him energetic and active to the end of his days. Many scientists all over the world, both young and old, will respond to Harold Ted Hammel’s death with deep sorrow. They have lost a man whose enthusiasm and original ideas were essential for them as guidance and incentive in their own scientific careers, and they will remember him with deep gratitude.
Eckhart Simon, M.D.
Emeritus Director of the Physiology Department
Max-Planck-Institute for Heart and Lung Research
Germany
E-mail: eckhart.simon@kerckhoff.mpg.de
"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
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Today I found that Professor Hammel has passed on.
Having spoken with him and discussed experiments and their results relating to water transport in trees. He agreed to help me to write a paper on a subject, which has been close to his heart for much of his working life and carried on being important to him right until the end. It was for this reason that I was searching to find his contact details to ask him to join our forum in order to offer his expert guidance.
Needless to say this is a very sad day for me, and a sad day for the world of enquiring minds.
It was his Old friend Michel Cabanac that suggested I contact Him and disclose my experiments and theory.
Professor Hammel received my introduction and patiently sat through my ramblings having already promptly replied sending a letter together with reprints of papers from his huge amount of research into this subject, in the hope that the papers would help to support my own work.
My conversation with Professor Hammel was well received; he had a tremendous amount of enthusiasm for the subject. Even though he had been retired for some years, his unbiased manner of conversing with me, and I guess many of his students friends, and even complete strangers who have undoubtedly engaged him over his years, as I did, have been captivated in his tenacity for scientific truth.
Although I never met him in person, and feel now robbed of the privilege forever, I shall remember him for the rest of my days as a kind and just man, who gave so much of his time to science.
Andrew Kenneth Fletcher
"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
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Letters to Doug Stewart
H. Ted Hammel writes: “Thank you for your query about my state of being and raison d’etre. When my friends inquire, ‘How are you?’ my usual response, in jest, has been, ‘Worse than ever.’ At 80 years of age, getting better than ever is unrealistic. More recently, my response to, ‘How are you?’ has become, ‘Apoptosic.’
“Until your letter, I had supposed that I had become persona non grata. Anyone daring to declare that Starling’s osmotic force is fiction, as I have done, must also know that the wagons of physiology will form the circle in defense against the ingnoramus. Of course, I know with certainty that Starling’s osmotic force cannot return ISF to the plasma of the capillary. This hypothetical force presumes that the colloidal proteins in plasma attract ISF, according to Starling, or they lower the concentrations of water in plasma, according to physiologists. Proteins do not act this way in plasma or in an osmometer. For more, see several of my articles on how solutes alter water in an aqueous solution. For example, 1) Hammel, H.T. (1994) “How solutes alter water in aqueous solutions. The Journal of Physical Chemistry. 98:4196-4204. 2) Hammel, H.T. (1998) ‘Replacing Lewis’s theory with Hulett’s theory of altered chemical potentials of reacting constituents in solution.’ Recent Research Developments in Physical Chemistry: 2, 77-111. (Pandalai, S.G., Ed.) Transworld Research Network, Trivandrum, India. 3) Hammel, H.T. Boltzmann’s principle depicts distribution of water molecules between vapor and liquid for pure liquid and for aqueous solutions. The Journal of Physical Chemistry. 99:8392-8400, 1995. 4) Hammel, H.T. (1999) Evolving ideas about osmosis and capillary fluid exchange. 5) Hammel, H.T. and Brechue, W.F. (2000). Plasma-ISF fluid exchange in tissue is drive by diffusion of carbon dioxide and bicarbonate in presence of carbonic anhydrase. FASEB J. 14: Abstract 315.3.
“I have written a monograph entitled ‘Better Understanding of Solutions: How Solute Alters Water and More.’ The monograph is in three parts. Part I is based on Hulett’s theory of osmosis and covers the period when Pete Scholander and I were collaborating. Part II is autobiographical and tells how I came to collaborate with Scholander. Part III covers the progress made during the last 20 years since collaboration with Scholander ceased at his death in 1980. At this time, the monograph has not been published and does not have a publisher. Maybe later.
“I have had engraved on my gravestone the following declaration: ‘A physiologist who measured xylem and phloem sap pressures in trees; who embraced Hulett’s theory of osmosis and who recognized the diffusion of bicarbonate ions as the principal osmotic effect in Starling’s hypothesis.’
“When Scholander and I finished our monograph on ‘Osmosis and Tensile Solvent’ in 1976, I said to him, ‘Pete, you will never know the day when our ideas about osmosis become widely accepted.’ Twenty-five years later, I repeat the same statement, now applied to myself. I feel obliged, therefore, to engrave our views in granite.”
http://www.the-aps.org/publications/tphys/2001html/October01/srphys.htm
"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
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Is this just copied from:
http://www.the-aps.org/publications/tphys/2001html/October01/srphys.htm
Are there copyright issues?
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Am J Physiol. 1995 May;268(5 Pt 2):H2133-44. Related Articles, Links
Roles of colloidal molecules in Starling's hypothesis and in returning interstitial fluid to the vasa recta.
Hammel HT.
Department of Physiology and Biophysics, Indiana University, Bloomington 47405, USA.
To begin to understand the role of colloidal molecules, a simple question requires an answer: How do the solutes alter water in an aqueous solution? Hulett's answer deserves attention, namely, the water in the solution at temperature and external pressure applied to solution (T,pe1) is altered in the same way that pure water is altered by reducing the pressure applied to it by the osmotic pressure of the water at a free surface of the solution. It is nonsense to relate the lower chemical potential of water in a solution to a lower fugacity or to a lower activity of the water in the solution, since these terms have no physical meaning. It is also incorrect to attribute the lower chemical potential of the water to a lower concentration of water in the solution. Both claims are derived from the teachings of G. N. Lewis and are erroneous. Textbook accounts of the flux of fluid to and from capillaries in the kidney and other tissues are inadequate, if not in error, as they are based on these bogus claims. An understanding of the process by which colloidal proteins in plasma affect the flux of nearly protein-free fluid across the capillary endothelium must start with insights derived from the teachings of G. Hulett and H. Dixon. The main points are 1) colloidal molecules can exert a pressure against a membrane that reflects them and, thereby, displace a distensible membrane; 2) they can alter the internal tension of the fluid through which they diffuse when there is a concentration gradient of the molecules; and 3) only by these means can they influence the flux of plasma fluid across the capillary endothelium. However, the process is complex, since both the hydrostatic pressure and protein concentrations of fluids inside and outside the capillary vary with both position and time as plasma flows through the capillary.
PMID: 7771564 [PubMed - indexed for MEDLINE]
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Dave, I know Professor Hammel would want to have this letter on a page commemorating his work and integrity. I have had a very long conversation with him about his work and his past work in other areas of physics.
It is befitting that he should have this text on display, and there does not appear to be any copyright attached to it, and as it is not for anyone’s financial gain, I can’t see any problem with placing it here.
Although I never met him, and never will, I feel I have known him all my life. Even in the text he expresses that his work should be remembered, and should anyone want to remove it with good cause, I can always hit the delete button.
After all, most of the information that is published on the Internet for all to see is by nature already in the public domain. Much of what is published from the Internet is done so by the copy and paste method.
How else are we supposed to remember people for what they have achieved in science without being able to show exactly what they have achieved throughout their lives?
I intend to make references to his work along with that of Pete Scholander
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In Memory of
Professor Harold T. Hammel, Ph.D.
March 4, 2005
Harold Ted Hammel, Ph.D. and Professor Emeritus, died on February 24, 2005 in his 84th year of life. After his academic education in Physics and Zoology/Zoophysiology, the stations of his career in physiology were the University of Pennsylvania, Philadelphia, the John B. Pierce Foundation Laboratory at New Haven, an institution associated with Yale University, and – until his retirement – the Physiological Research Laboratory of the Scripps Institution at La Jolla, where he also served as Professor of Physiology of the University of California, San Diego. After his retirement he remained active as an Adjunct Professor of the Human Biology Department of the University of Indiana at Bloomington. The field of research to which H.T. Hammel made his first internationally recognized contributions, was adaptation of humans to extreme climatic conditions. His field studies done in co-operation with the late P.F. Scholander on indigenous populations (Kalahari Bushmen, Australian Aborigines and Alacaluf Indians at Tierra del Fuego) will forever maintain their value as unique documents of the strategies of adaptation to cold developed by these populations living under very different conditions of cold exposure and food supply. H.T. Hammel has become world-famous by his work on the hypothalamus of homeotherms for which he was the first to quantify its thermosensory function as input signal into the natural feedback system of thermoregulation. His results stimulated laboratories all over the world to proceed on the basis of his discoveries and, in particular, they served as the touchstone for the experimental approach to deep-body thermosensitivity in general, leading ultimately to the current concept of thermoregulation as a multiple-input/multiple-effector feedback system. Cooperation of H.T. Hammel with the Department of Physiology, Max-Planck-Institute for Physiological and Clinical Research (now Heart and Lung Research), W.G. Kerckhoff-Institute, Bad Nauheim, Germany, had been initiated as early as 1963 on the occasion of field studies on human cold tolerance in the Highlands of Southern Norway (Hardanger-Vidda). It culminated first in common work on thermo- and osmoregulation of the Adelie Penguin during an Expedition to McMurdo, Antarctica in 1975. Further joint research was put on an official basis, when H.T. Hammel was elected in 1978 as External Scientific Member of the Max-Planck-Institute at Bad Nauheim. This appointment not only has been held by him in great esteem, but it started the period of his continuing collaboration with researchers of this institute’s Physiology Department in the fields of thermo-and osmoregulation. During 12 successive years, until his retirement, H.T. Hammel spent between 3 and 6 months every year at Bad Nauheim, often accompanied by his wife Dorothy, making important contributions to the analysis of salt and fluid balance, one of the department’s main fields of research. Above all, however, water as the medium of life has remained in the focus of H.T. Hammel’s interest from the start to the end of his life as a scientist. In animals and plants he has continuously studied and analyzed water transport induced by evaporation and osmosis. Based on seminal experiments and on decades of thinking he developed his original hypothesis of altered water tension underlying the phenomena of water transport and he has continued to refine the presentation of his concept. The controversy with proponents of the classical theory of the colligative properties of water, in which he slowly but continuously has gained ground, had become his “elixir of life” keeping him energetic and active to the end of his days. Many scientists all over the world, both young and old, will respond to Harold Ted Hammel’s death with deep sorrow. They have lost a man whose enthusiasm and original ideas were essential for them as guidance and incentive in their own scientific careers, and they will remember him with deep gratitude.
Eckhart Simon, M.D.
Emeritus Director of the Physiology Department
Max-Planck-Institute for Heart and Lung Research
Germany
E-mail: eckhart.simon@kerckhoff.mpg.de
http://www.feverlab.net/meeting/memory_hammel.htm
Link to original article source: http://feverlab.net/pages/people/History.html
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In Memory of
Professor Harold T. Hammel, Ph.D.
March 4, 2005
Harold Ted Hammel, Ph.D. and Professor Emeritus, died on February 24, 2005 in his 84th year of life. After his academic education in Physics and Zoology/Zoophysiology, the stations of his career in physiology were the University of Pennsylvania, Philadelphia, the John B. Pierce Foundation Laboratory at New Haven, an institution associated with Yale University, and – until his retirement – the Physiological Research Laboratory of the Scripps Institution at La Jolla, where he also served as Professor of Physiology of the University of California, San Diego. After his retirement he remained active as an Adjunct Professor of the Human Biology Department of the University of Indiana at Bloomington. The field of research to which H.T. Hammel made his first internationally recognized contributions, was adaptation of humans to extreme climatic conditions. His field studies done in co-operation with the late P.F. Scholander on indigenous populations (Kalahari Bushmen, Australian Aborigines and Alacaluf Indians at Tierra del Fuego) will forever maintain their value as unique documents of the strategies of adaptation to cold developed by these populations living under very different conditions of cold exposure and food supply. H.T. Hammel has become world-famous by his work on the hypothalamus of homeotherms for which he was the first to quantify its thermosensory function as input signal into the natural feedback system of thermoregulation. His results stimulated laboratories all over the world to proceed on the basis of his discoveries and, in particular, they served as the touchstone for the experimental approach to deep-body thermosensitivity in general, leading ultimately to the current concept of thermoregulation as a multiple-input/multiple-effector feedback system. Cooperation of H.T. Hammel with the Department of Physiology, Max-Planck-Institute for Physiological and Clinical Research (now Heart and Lung Research), W.G. Kerckhoff-Institute, Bad Nauheim, Germany, had been initiated as early as 1963 on the occasion of field studies on human cold tolerance in the Highlands of Southern Norway (Hardanger-Vidda). It culminated first in common work on thermo- and osmoregulation of the Adelie Penguin during an Expedition to McMurdo, Antarctica in 1975. Further joint research was put on an official basis, when H.T. Hammel was elected in 1978 as External Scientific Member of the Max-Planck-Institute at Bad Nauheim. This appointment not only has been held by him in great esteem, but it started the period of his continuing collaboration with researchers of this institute’s Physiology Department in the fields of thermo-and osmoregulation. During 12 successive years, until his retirement, H.T. Hammel spent between 3 and 6 months every year at Bad Nauheim, often accompanied by his wife Dorothy, making important contributions to the analysis of salt and fluid balance, one of the department’s main fields of research. Above all, however, water as the medium of life has remained in the focus of H.T. Hammel’s interest from the start to the end of his life as a scientist. In animals and plants he has continuously studied and analyzed water transport induced by evaporation and osmosis. Based on seminal experiments and on decades of thinking he developed his original hypothesis of altered water tension underlying the phenomena of water transport and he has continued to refine the presentation of his concept. The controversy with proponents of the classical theory of the colligative properties of water, in which he slowly but continuously has gained ground, had become his “elixir of life” keeping him energetic and active to the end of his days. Many scientists all over the world, both young and old, will respond to Harold Ted Hammel’s death with deep sorrow. They have lost a man whose enthusiasm and original ideas were essential for them as guidance and incentive in their own scientific careers, and they will remember him with deep gratitude.
Eckhart Simon, M.D.
Emeritus Director of the Physiology Department
Max-Planck-Institute for Heart and Lung Research
Germany
E-mail: eckhart.simon@kerckhoff.mpg.de
<font color="brown"><font size="1">"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"</font id="size1"></font id="brown">
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http://www.fasebj.org/cgi/content/full/13/2/213
Evolving ideas about osmosis and capillary fluid exchange 1
H. T. HAMMEL 2
Department of Physiology and Biophysics, Medical Sciences Program, Indiana University School of Medicine, Bloomington, Indiana 47405-4401, USA
ABSTRACT
When a solute is dissolved in water at (T, pel), the temperature and external pressure applied to the solution, the water in the solution is altered as is pure liquid water at (T, pel - {pi}H2Ol). The liquid water and the water in the solution are in equilibrium when {pi}H2Ol is the osmotic pressure of the water in the solution. Every partial molar property of the water in the solution at (T, pel), including its vapor pressure, chemical potential, volume, internal energy, enthalpy and entropy, is identical with the same molar property of pure liquid water at (T, pel - {pi}H2Ol). This elementary fact was deduced by Hulett in 1903 from a thought experiment; he concluded that the internal tension in the force bonding the water is the same in both solution and pure liquid water, in equilibrium, at these differing applied pressures. Hulett's understanding of osmosis and the means by which the water was altered by the solute were neglected and abandoned. Competing ideas included the notions that the solute attracts the water into the solution and that the solute lowers the activity (or concentration) of the water in the solution. These ideas imply that the solute acts on the solvent at the semipermeable membrane separating the solution and water. Hulett's theory of osmosis requires that the solute alter the water at the free surface of the solution where the solute exerts an internal pressure on the boundary of the solution retaining the solute. Fluid exchange across the capillary endothelium is influenced, in part, by colloidal proteins in the plasma. The role of the proteins in capillary fluid exchange must be reinterpreted based on Hulett's view, the only valid view of osmosis.—Hammel, H. T. Evolving ideas about osmosis and capillary fluid exchange.
http://www.fasebj.org/cgi/content/full/13/2/213
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http://www.yarbroughlaw.com/Patent%20Projects/publications%20of%20HT%20Hammel.htm
Partial List of Publications of the late
Harold T. Hammel, Ph.D
Photo of H.T. Hammel, Ph.DThe following is a partial list of the late Dr. Harold T. Hammel's publications in the area of osmosis. Follow this link to an introduction to Dr. Hammel's ideas. Follow this link to a patent application addressing high altitude pulmonary edema ("HAPE").
1) Hammel, H.T. and Scholander, P.F. (1973) Thermal Motion and Forced Migration of Colloidal Particles Generate Hydrostatic Pressure in a Solvent PNAS, Jan 1973; 70:124-128
2) Alan R.Hargens, Lemuel J. Bowie, Deborah Lent, Sylvester Carreathers, Richard M. Peters, H. T. Hammel, and P. F. Scholander (1980) Sickle-Cell Hemoglobin: Fall in Osmotic Pressure upon Deoxygenation PNAS, Jul 1980; 77: 4310 - 4312.
3) Hammel HT and AR Hargens, (1986) Mechanism of Osmosis: Hulett's vs. Lewis' View of Altered Solvent in Solution. Frontiers in Biomechanics, edited by GW Schmid-Schoenbein, SL-Y Woo, and BW Zweifach. New York: Springer-Verlag, pp. 142-149
4) Hammel, H. T. (1994) How solute alters water in aqueous solutions. J.Phys.Chem. 98: 4196-204.
5) Hammel, H. T. (1995) Role of colloidal molecules in Starling’s hypothesis and in returning interstitial fluid to the vasa recta. Am. J. Physiol. 268:H2133-44.
6) Hammel, H.T. (1998) Replacing Lewis's theory with Huletts theory of altered chemical potentials of reacting constituents in solution. Recent Res. Devel. in Physical Chem. 2:77-111.
7) Hammel, H. T. (1999) Evolving ideas about osmosis and capillary fluid exchange. FASEB J. 13: 213-231.
8) Hammel, H. T., Brecheu, W. F. (2000) Plasma-ISF fluid exchange in tissue is driven by diffusion of carbon dioxide and bicarbonate in presence of carbonic anhydrase. FASEB 14: Abstract 315.3.
9) Brecheu, W. F., Hammel, H. T. (2002) Causes of plasma-ISF exchange in fish, birds and mammals. FASEB J. 16: Abstract 657.1.
10) Hammel, H.T., Schlegel, WM (2005) Osmosis and solute-solvent drag: fluid transport and fluid exchange in animals and plants, Cell Biochem Biophys 42(3):277-345
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The obituary by Prof. Eckhart Simon posted on this forum by Andrew K. Fletcher and others was written for the http://www.feverlab.net website, in connection with the Second International Meeting of Physiology and Pharmacology of Temperature Regulation that took place in Phoenix, AZ, USA, on March 3-6, 2006 (http://feverlab.net/pages/publicationpdfs/Meeting_PPTR.html). This obituary is now moved to http://feverlab.net/pages/people/History.html. Anyone quoting this obituary should include a link to this page. The same page contains links to two other pieces about Prof. Hammel: enjoy!
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The obituary by Prof. Eckhart Simon posted on this forum by Andrew K. Fletcher and others was written for the http://www.feverlab.net website, in connection with the Second International Meeting of Physiology and Pharmacology of Temperature Regulation that took place in Phoenix, AZ, USA, on March 3-6, 2006 (http://feverlab.net/pages/publicationpdfs/Meeting_PPTR.html). This obituary is now moved to http://feverlab.net/pages/people/History.html. Anyone quoting this obituary should include a link to this page. The same page contains links to two other pieces about Prof. Hammel: enjoy!
Have included the link as per your instructions. Thanks for informing us of the now moved article.
Do you have any photographs of Ted that can be added to this thread?
Best
Andrew
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Titre du document / Document title
Osmosis and solute-solvent drag : Fluid transport and fluid exchange in animals and plants
Auteur(s) / Author(s)
HAMMEL H. T. ; SCHLEGEL Whitney M. ;
Résumé / Abstract
In 1903, George Hulett explained how solute alters water in an aqueous solution to lower the vapor pressure of its water. Hulett also explained how the same altered water causes osmosis and osmotic pressure when the solution is separated from liquid water by a membrane permeable to the water only. Hulett recognized that the solute molecules diffuse toward all boundaries of the solution containing the solute. Solute diffusion is stopped at all boundaries, at an open-unopposed surface of the solution, at a semipermeable membrane, at a container wall, or at the boundary of a solid or gaseous inclusion surrounded by solution but not dissolved in it. At each boundary of the solution, the solute molecules are reflected, they change momentum, and the change of momentum of all reflected molecules is a pressure, a solute pressure (i.e., a force on a unit area of reflecting boundary). When a boundary of the solution is open and unopposed, the solute pressure alters the internal tension in the force bonding the water in its liquid phase, namely, the hydrogen bond. All altered properties of the water in the solution are explained by the altered internal tension of the water in the solution. We acclaim Hulett's explanation of osmosis, osmotic pressure, and lowering of the vapor pressure of water in an aqueous solution. His explanation is self-evident. It is the necessary, sufficient, and inescapable explanation of all altered properties of the water in the solution relative to the same property of pure liquid water at the same externally applied pressure and the same temperature. We extend Hulett's explanation of osmosis to include the osmotic effects of solute diffusing through solvent and dragging on the solvent through which it diffuses. Therein lies the explanations of (1) the extravasation from and return of interstitial fluid to capillaries, (2) the return of luminal fluid in the proximal and distal convoluted tubules of a kidney nephron to their peritubular capillaries, (3) the return of interstitial fluid to the vasa recta, (4) return of aqueous humor to the episcleral veins, and (5) flow of phloem from source to sink in higher plants and many more examples of fluid transport and fluid exchange in animal and plant physiology. When a membrane is permeable to water only and when it separates differing aqueous solutions, the flow of water is from the solution with the lower osmotic pressure to the solution with the higher osmotic pressure. On the contrary, when no diffusion barrier separates differing parts of an aqueous solution, fluid may flow from the part with the higher osmotic pressure to the part with the lower osmotic pressure because the solute molecules diffuse toward their lower concentration and they drag on the water through which they diffuse. This latter osmotic effect (diffusing solute dragging on solvent or counterosmosis) between differing parts of a solution has long been neglected and ignored when explaining fluid fluxes in plant and animal physiology. For two solutions separated by a semipermeable membrane, osmosis is the flow of its solvent from the solution with the lower solute concentration into the solution with the higher solute concentration. For two contiguous solutions not separated by a semipermeable membrane, counterosmosis is the flow of solution with the higher solute concentration toward the solution with the lower solute concentration.
Revue / Journal Title
Cell biochemistry and biophysics ISSN 1085-9195 CODEN CBBIFV