Title: The cell and protoplasm ..
Identifier: cellprotoplasm00amer (find matches)
Year: 1940 (1940s)
Authors: American Association for the Advancement of Science; Moulton, Forest Ray, 1872-1952
Subjects: Cells; Protoplasm; Cytology; Cytoplasm
Publisher: Washington, Pub. for the American asscoiation for the advancement of science by the Science press
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
&â -h + Fig. 1A. Single ionic particles with ionic atmos- phere (ions of opposite sign not shown). It is difficult to explain the presence of any structure in a cell containing 80 to 90 per cent of water, and until very recently all hypotheses as to intracellular structure, fibers, foams, etc., could not receive any physicochemical explanations, as the ac- tual structures observed were in most cases artefacts plainly due to the method of preparation of the specimen. We now have, however, what may be the first clue to the intercellular structures of this intermediate degree of complexity. Theoretical studies of colloids, particularly those of Langmuir and Levine, combined with the quantitative data provided by the oriented sols of tobacco mosaic virus have shown indisputably that interparticle forces sufficient to maintain structures against thermal agitation do exist and that they are susceptible to quantitative theo- retical explanation. These long-range forces have long been suspected, but the mechanism previously proposed for them, polarization of water molecules (London Van der Waals forces) were plainly physi- cally unacceptable. The clue to the nature of these forces was found in the ionic at- mospheres which, according to the Debye- Hiickel theory, nuist surround every charged particle in an electrolyte. For a large particle, such as a protein molecule, this atmosphere extends to a distance of the order of a few times the particle diam- eter (Fig. 1). AVhen two such particles ai^proach one another, the interaction of the charges of each particle on the atmos- phere of the other produces, at great dis- tances, an attractive force; at smaller dis- tances the interpenetration of the atmos- pheres makes this force repulsive. In gen- eral the interaction between the two par- ticles can be expressed by the familiar potential energy curve (Fig. 1 D) which -f-
Text Appearing After Image:
+ -4- -

Note About Images