The Herter lectures (New York, 1908) on the fluids of the body.

  • Starling, Ernest Henry, 1866-1927.
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: The Herter lectures (New York, 1908) on the fluids of the body. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    of many permanent suspensions. Although we have no evidence that the size of a molecule is arithmetically propor- tional to its molecular weight, there is no doubt that the size must be a function of the molecular weight and must increase with the latter. A molecule with a molecular weight of 100,000, although probably not directly visible with the micro- scope, might have a refractive index differing from the surrounding medium ; like a particle of dust in the familiar Tyndall experiment it would scatter rays of light, and might therefore be rendered visible by some method of illumination such as that adopted in the ultra-microscope of Zigmondy. But such huge molecules can no longer be expected to follow exactly the laws which have been derived from the study of the behaviour of the almost perfect gases and similar substances. In these the size of a molecule under ordinary conditions is negligible compared with the distance between each molecule, so that each molecule may be regarded as a point of force. Molecules of the size we have suggested would possess the properties of matter in mass. They would have a surface of measurable extent, and their relation to the molecules of the Vv^ater, or solvent surrounding them, would l)e determined by the laws of adsorption rather than by the laws of interaction of molecules. As a matter of fact we find that the solutions of the different colloids which make up the animal cell present an amazing mixture of properties, some of which betray them as mechanical suspensions, while others partake of the nature of chemical reactions, such as those usually dealt with by the chemist. Let us briefly consider some of the distinguishing features of such solutions. It has been hotly debated whether a colloidal solution, or sol, is to be regarded as a solution at all, or as a suspension. The chief criterion of a true solution is its homogeneity. In a solution the molecules of the solute