. Principles of modern biology. Biology. Fig. 4-22. Emulsion formed from olive oil and water, as seen with the microscope; the oil contains a dye to make it darker. The changes in form of an emulsion are brought about by the addition of small amounts of a substance that changes the chemical constitution of the emulsifying agent. A, water the continuous phase, oil the discontinuous (dispersed) phase. B, intermediate form, the emulsion "breaking"; this state is very unstable, the two phases being in continual rapid motion and rearrangement. C, oil the continuous phase, water the dis- p
. Principles of modern biology. Biology. Fig. 4-22. Emulsion formed from olive oil and water, as seen with the microscope; the oil contains a dye to make it darker. The changes in form of an emulsion are brought about by the addition of small amounts of a substance that changes the chemical constitution of the emulsifying agent. A, water the continuous phase, oil the discontinuous (dispersed) phase. B, intermediate form, the emulsion "breaking"; this state is very unstable, the two phases being in continual rapid motion and rearrangement. C, oil the continuous phase, water the dis- persed phase. of the protoplasm are due to such phase re- versals, which result from chemical changes wrought by the metabolism of the cell, or from chemical changes in the nearby envi- ronment. Gelation and Solation. Protoplasm fre- The capacity to gelate is found in many colloidal systems, especially when the dis- persed particles are elongate, like protein or polysaccharide molecules. In the sol condi- tion such elongate particles behave more or less as separate units (Figs. 4-23A). But as quently alters its consistency by undergoing gelation occurs, attractive forces come into gelation or solation. Like a gelatin solution, the fluid protoplasm of a cell may become set at a certain moment into a semisolid elastic mass; and then later it may revert to a more fluid consistency. Recently the func- tion of these changes has become clearer. The evidence indicates that the contractility of protoplasm depends upon its capacity to undergo gelation; and that many cell move- ments, such as amoeboid movement, cannot occur if the sol-gel changes in the protoplasm are Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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