Volume 1

A text-book of physiology / by Henry P. Bowditch [and others] ; edited by William H. Howell.

Date:
1900
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: A text-book of physiology / by Henry P. Bowditch [and others] ; edited by William H. Howell. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    579/608 (page 575)
    blood-plasma, butter, egg-yolk, and of fat; likewise visual jjurple of the retina, which is bleached by light. Solutions of the pure visual purple from rabbits or dogs become clear as water on exposure to light. ^ Oholesterin. Cholesterin, CjtH^jOH.—This is found in all animal and vegetable cells and in the milk.'' It is especially present in nervous tissue and in blood-corpuscles. It is excreted through the bile and through the intestinal wall.^ In the blood-plasma it is present as an ester combined with oleic and palmitic acids, while in the corpuscle it occurs as simple cholesterin.'' It may be prepared by dissolving gall-stones in hot alcohol, from which solution the cholesterin crystallizes on cooling in characteristic plates. It is insoluble in water or acids, but soluble in the biliary salts, ether, and hot alcohol. It is probably not absorbed by the intestinal canal. In human feces stercorin appears instead of choles- terin.^ This stercorin (the koprosterin of Bondzynski) is a dihydrocholesterin, CjtH^OH, and is the result of putrefactive change.' Cholesterin feels like a fat to the touch, but is in reality a moiiatomic alcohol. With concentrated sulphuric acid it yields a hydrocarbon, cholesterilin, C.28H4.,, coloring the sulphuric acid red (Salkowski's reaction). Iso-cholesterin, an isomere, is found combined as an ester with fatty acid in wool-fat or lanolin. The physiological imi^oi-tance of cholesterin is unknown. The Proteids. Consideration of the proteids from a purely chemical standpoint is impos- sible, for their composition is unknown. There exist only the indices of com- position furnished by tlie products of cleavage and disintegration. Bodies at present classed as individuals may sometimes be shown to be identical, with characterizing impurities. It remains for the chemist to do for the proteid group what Emil Fischer with plienyl-hydrazin has accomplished for the sugars. As a characteristic proteid, egg-albumin may be mentioned. Proteid forms (after water) the largest part of the organized cell, and is found in all the fluids of the body except in urine, sweat, and bile. Proteid contains carbon, hydrogen, nitrogen, oxygen, sulphur, sometimes phosphorus and iron. General Reactions.—A neutral solution of proteid (with the exception of the peptones and proteoses) is partially precipitated on boiling, and is quite completely precipitated on careful addition of an acid (acetic) to the boiling solution. Proteids are precipitated in the cold by nitric and the other com- mon mineral acids, by metaphosphoric but not by orthophosphoric acid. Metallic salts, such as lead acetate, copper sulphate, and mercuric chloride, precipitate proteid; as do ferro- and ferricyanide of potassium in acetic-acid solution. Further, saturation of acid solutions of proteid with neutral salts (NaCl, NajSO^, (NHJjSOJ precipitates them, as does likewise alcohol in 1 Kiihne : Zeitschrift fur Biologic, 1895, Bd. 32, S. 26. 2 Schmidt-Miihlheim: Pfluger's Archiv, 1883, Bd. 30, S. 384. ' Moraczew.ski: Zeitschrift fiir physiologische Chemie, 1898, Bd. 25, S. 122. * Hepner: Pfliiger's Archiv, 1898, Bd. 73, S. 595. ^ Flint: American Journal of Medical Sciences, ] 862. ^ Bondzynski and Humnicke: Zeitschrift fur physiologische Chemie, 1896, Bd. 22, S. 396. ' Miiller, P.: Ibid., 1900, Bd. 29, S. 129.