File:A text-book on physiology - for the use of schools and colleges - being an abridgment of the author's larger work on human physiology (1866) (14581434320).jpg

Identifier: textbookonphysio00drap (find matches)
Title: A text-book on physiology : for the use of schools and colleges : being an abridgment of the author's larger work on human physiology
Year: 1866 (1860s)
Authors: Draper, John William, 1811-1882
Subjects: Human physiology Physiology
Publisher: New York : Harper & Bros.
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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more readiness, some with less,the result in these respects depending on the electro-chemical relations subsisting between them and the solidthey are in contact with, and their own force of cohe-sion ; that organic membranes present no peculiarities,their action arising, not because they are organic, butbecause they are porous; that the so-called selectingpower is purely physical, as are the separations and ap-parent decompositions to which it gives rise. When adrop of colored water is put upon chalk, the water sinksin, but the color is left on the surface. When weak al-cohol is tied up in a bladder, the water will escapethrough the pores, and the spirit become anhydrous atlast. If we take a glass tube, a a, Fig. 30 (page 90), overthe lower end of which a piece of peritoneum, or otherdelicate membrane, b 5, is tightly tied, and half fill it With what force do these motions of liquids take place? Howmay the selecting power of membranes be illustrated ? 90 SELECTING POWER OF MEMBRANES.
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with litmus water, and then place it ina glass of alcohol, c c, the level of theliquids inside and outside being adjust-ed according to their specific gravity, sothat there may be no hydrostatic press-ure either one way or the other throughthe pores of the peritoneum—as soon asthe arrangement is completed, if the ob-server be so placed as to view it bytransmitted light, he will see the waterdescending from the pores of the peri-toneum in striae and streams throughthe alcohol in a perfectly colorless state.The membrane, therefore, has absorbedand transmitted the water, but has re-fused to the coloring matter a passage.It is to this particular experiment thatallusion was made when speaking of thenon-coloration of the chyle after certaincoloring material had been mixed withthe food. Such illustrations may there-fore satisfy us that the selecting powerof organic porous textures, like that ofinorganic ones, is dependent on simple physical circum-stances. In view of all the preceding fact

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