Life at the Cell and Below-Cell Level. The Hidden History of a Fundamental Revolution in Biology
Gilbert N. Ling, Ph.D.
Pacific Press
ISBN 0-9707322-0-1

"Dr. Ling is one of the most inventive biochemist I have ever met."
Prof. Albert Szent-Györgyi, Nobel Laureate

Chapter 3.

How the Membrane Theory Began
(p. 10-13)

Moritz Traube (1826-1894), a Berlin tradesman and amateur research scientist, made an elementary but history-making discovery.17 When a drop of copper sulfate solution is brought into contact with a drop of potassium ferrocyanide solution, a thin layer of reddish-brown copper-ferrocyanide precipitate forms at, and blankets, the entire boundary. After that, no further formation of precipitate occurs. Thus the thin layer of precipitated material formed between the two drops of solutions has halted further passage to the other side of the copper ion as well as the ferrocyanide ion.

Traube published his finding in 1867.17 Its significance was promptly recognized by Wilhelm Pfeffer. By allowing the copper ferrocyanide precipitate to form within the wall of a porous porcelain cylinder, Pfeffer transformed Traube's fragile layer of copper-ferrocyanide precipitate into a practical experimental model strong enough to withstand not only routine handling but even unilateral application of mechanical pressure. Placing sucrose solutions of different strengths on either side of such a fortified copper-ferrocyanide membrane, he saw water moving from the dilute to the concentrated side18reminiscent of what Abbe Nollet witnessed across his dead animal membrane and what Dutrochet observed in and out of living mature plant cells.

Pfeffer also found that this osmotic water movement could be brought to a stop by applying to the side containing the more concentrated sucrose solution a pressure of just enough strength (to be referred to as osmotic pressure). Now if one side contains sucrose solutions of different concentrations (represented as C) and the other side contains plain water, or if the temperature was varied while is held constant, then the osmotic pressure, , was shown to be proportional to C, and to the absolute temperature, T, respectively.18

Dutch botanist, Hugo de Vries (1848-1935), who introduced the important mutation theory to genetics,363 p 34 brought Pfeffer's exciting findings to the attention of physico-chemist, J. H. van't Hoffwhose name was mentioned above. Not long after, van't Hoff discovered that an equation resembling the perfect gas law (i.e., PV = RT, where P is the pressure applied to a (perfect) gas occupying a volume, V, at the absolute temperature, T and R is the gas constant) could correctly predict both sets of relationships Pfeffer's meticulous work had brought to light:

π V = R' T   (1)

where V is the volume of solution containing one mole of sucrose and thus equal to 1/C. n, T have the meanings given above. R' is a constant. Substituting Pfeffer's experimentally determined values of 71, V (= 1/C) and T into Equation 1, van't Hoff obtained the constant R', which in numerical value, is close to that of the gas constant, R (1.987 cal. deg.-1 mole-1).

For the origin of the osmotic pressure, van't Hoff introduced his bombardment theory. Pointing out the analogy of the perfect gas law and the van't Hoff equation shown above (Equation 1), he wrote: "In the former case, the pressure is due to the impacts of gaseous molecules on the walls of the containing vessel, and in the latter to the impacts of the molecules of dissolved substance on the semipermeable membrane."13 p 664; 14 (For unexpected later developments, see [11.3 (7)].)

Thus Pfeffer's accurate study of osmotic pressure paved the way for what is often referred to as van't Hoffs solution theory. Continued investigations on both model systems and living (mature) plant cells led Pfeffer to ideas on the living plant cells, which were later referred to as Pfeffer's membrane theory (see below).

 Pfeffer published his major work in 1877 in a monograph entitled: "Osmotische Untersuchungen" ("Osmotic Investigations").18 In this volume, his main theme was that a peripheral layer of the protoplasm called Plasmahaut ("protoplasm skin" as one meaning of the word, plasma, is protoplasm)404 p 879 or plasma membrane covers not only the outer surface of the cell but any exposed surface of protoplasm where it comes into contact with "another aqueous solution." 18 p 234 And that a plasma membrane exhibits properties similar to those of the copper-ferrocyanide precipitation membrane. And that it is the universal presence of this enclosing plasma membrane that endows all living cells with its semipermeable properties and osmotic behaviors.

 In "Osmotische Untersuchungen" Pfeffer made no specific mention of the physicochemical nature of the cell content, nor did he mention Schwann by name. Yet in this monograph one comes upon a phrase here and another one there, each suggesting that, like Schwann, he too believed that the cell content has the property of an aqueous solution. Thus by referring to an aqueous solution in contact with the protoplasm as "another aqueous solution" just cited above, he offered one hint. He offered a second hint in his Summary of the second and last section entitled "Physiological Part" in these words: "Since protoplasm is also delimited from the cell sap by a plasma membrane, the cell osmotically resembles a system formed out of two cells of different sizes filled inside each other"18, 1885 p 235reminiscent of Schwann's "one hollow cell inside another hollow cell" imagery. Yet the smaller "cell" is unquestionably filled with an aqueous solution (the cell sap) and the larger one with protoplasm. If Pfeffer saw fundamental differences between the two contents, he made no mention of it.

The membrane theory has been widely attributed to Pfeffer, even though the term, membrane theory, was not cited in Pfeffer's "Osmotische Untersuchungen" published in 1877 nor in the second edition reissued unaltered in 1921, long after Pfeffer had "moved away" from the study of osmosis.18 pp ii-xxiii

 The long history of visualizing living cells as fluid-filled vesicles, buttressed by the elegant solution theory of van't Hoff, provided what appeared to be an unshakable foundation for the membrane theory. Additional evidence came from early osmotic studies and from investigators in other specialized fields of cell physiology. They include Julius Bernstein, author of the membrane theory of cellular electrical potentials19 and Frederick Donnan, author of the theory of membrane equilibrium of ionic distribution and electrical potential.20 That these theories and their corroborative evidence indeed offer support for the membrane theory, follows from the fact that they share the same fundamental assumption that living cells are membrane-enclosed dilute solutions.

The interweaving theories summarized above have also conjointly made the membrane theory the first coherent general theory of cell physiology. This theory can explain on the basis of the simple postulation of living cells as membrane-enclosed dilute solutions, four major subjects of cell physiology: (i) cell volume control, (ii) selective solute distribution, (iii) selective solute permeability and (iv) cellular electrical potentials.

In Chapter 4 immediately following, I shall examine the major supportive evidence for the membrane theoryfocused primarily on the existence of a semipermeable cell membraneas well as what has become of them eventually. Supportive evidence for free cell water and free cell potassium ion (K+) came later and will be presented in Chapter 5.

"Life at the Cell and Below-Cell Level.
The Hidden History of a Fundamental Revolution in Biology":

Contents (PDF 218 Kb)
Preface (
PDF 155 Kb)
Answers to Reader's Queries (Read First!) (
PDF 120 Kb)

1. How It Began on the Wrong Foot---Perhaps Inescapably
2. The Same Mistake Repeated in Cell Physiology
3. How the Membrane Theory Began
4. Evidence for a Cell Membrane Covering All Living Cells
5. Evidence for the Cell Content as a Dilute Solution
6. Colloid, the Brain Child of a Chemist
7. Legacy of the Nearly Forgotten Pioneers
8. Aftermath of the Rout
9. Troshin's Sorption Theory for Solute Distribution
10. Ling's Fixed Charge Hypothesis (LFCH)
11. The Polarized Multilayer Theory of Cell Water
12. The Membrane-Pump Theory and Grave Contradictions
13. The Physico-chemical Makeup of the Cell Membrane
14. The Living State: Electronic Mechanisms for its Maintenance and Control
15. Physiological Activities: Electronic Mechanisms and Their Control by ATP, Drugs, Hormones and Other Cardinal Adsorbents
16. Summary Plus
17. Epilogue 

A Super-Glossary
List of Abbreviations
List of Figures, Tables and Equations
References (
PDF 193 Kb)
Subject Index
About the Author

"Life at the Cell and Below-Cell Level..."
"Gilbert Ling"