A textbook of human physiology / translated from [the] 6th German edition by W. Stirling.

  • Landois, Leonard
Date:
1888
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Licence: Public Domain Mark

Credit: A textbook of human physiology / translated from [the] 6th German edition by W. Stirling. Source: Wellcome Collection.

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

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    to 64-5° (Sta7'le). It is changed into syntonin or acid-albumin by the action of dilute HCl, and by dilute alkalies into alkali-albuminate. Serum-albuniiu is absent from the blood of starving snakes; and reappears after they arc fed {Tiecjd). , , , [Serum-Albumin v. Egg-Albumin.—Although serum-albumin is closely related to egg- albumin they dilfer—(«) as regards their action upon polarised light; {h) tlie precipitate pro- duced by adding HCl or HNO3 is readily soluble in 4 c.c. of the reagent in the case of serum- albumin, wlule the precipitate in cgg-albumiii is dissolved with very great difficulty ; (c) egg- albumin, injected into the veins, is excreted in the urine as a foreign body, while scrum-albumin is not; [d) serum-albumin is not coagulated by ether, Avliile egg-albumin is, if the solution is not alkaline (§ 249). Serum-albumin has never been obtained free from salts, even when it is dialysed for a very long time.] After all the serum-globulin in serum is precipitated by magnesium sulphate, serum-albumin still remains in solution. If this solution be heated to 40 or 50° C. a copious precipitate of non-coagulated serum-albumin is obtained, which is soluble in water. If the serum-albumin be filtered from the fluid, and if the clear fluid be heated to over 60° C., Frederick found that it becomes turbid from the precipitation of other proteids ; the amount of these other bodies, however, is small. [Proteids of the Serum.—Halliburton has shown by the method of fractional heat-coagulation (^.e., ascertaining the temperature at which a proteid is roagulated, filtering the fluid and again heating the filtrate to a higher temperature), that from the same fluid perhaps two or more proteids, all with different tempera- tures of coagulation, may be obtained. Care must be taken to keep the reaction constant. He finds that serum-globulin coagulates at 75° C, while serum-albumin in reality consists of three proteids, which coagulate at different temperatures ; (<z) at 73°, {13) at 77°, and (y) at 84° C] [Precipitation by Salts.—Sulphate of magnesia not only precipitates serum-globulin but also fil)rinogen. The fluid must be shaken for several hours to get complete saturation. Sodic sulphate, Mhen added to serum deprived of its globulin by MgSO^, precipitates serum-albumin, luit it produces no precipitate with pure serum. In this way serum-albumin may be obtained in a pure, uncoagulated, and still soluble condition. Serum-globulin is thrown down by sodic nitrate, acetate, or carbonate ; while all the proteids of the serum are precipitated hy potassic acetate or phosphate, and the same result is bronght about by adding two salts, e.g., MgSO^ and Na.jSOj (in this case sodio-magnesic sul])hate is formed); MgS04 and ISTai^O;,; JIgS04 and KI ; NaCl and Na^SOj. After serum-globulin is thrown down by ]MgS04, the addition of MgS04 ^^^fl Na^S04 or the double-salt, precipitates the serum-allnunin, which is still soluble in water. As sulphate of ammonia precipitates all the proteids except peptones, it may be used (Hamhoion).] [The plasma of Invertebrata (decapod crustaceans, some gasteropods, cephalopods, &c.) clots like vertebrate blood, and contains fibrinogen, but, in addition, there is found in it a substance corresponding to Inemoglobin, and called by Fredericq, hsemocyanin. It exists like Hb in two conditions, one reduced and the other oxy-ha-mocyanin, the former being colourless,.the latter blue. In its general characters it resembles Hb, although it contains coiipcr instead of iron, and gives no absorption-bands {Halliburton). In the blood of some decapod crustaceans there is a reddish pigment, tetronerythrin, which is identical with that in the exoskeleton and hypodenn. It belongs to the group of lipochroraes, like some of the pigments of the retina. The hasmocyanin is respiratory in function, and it is remarkable that it is contained in the plasma, and not in the formed elements like the Hb of vertebrates. So that, stated broadly, in these invertebrates the plasma is both nutritive and respiratory in its functions, while in vertebrates the red corpuscles chiefly arc rcs]iiratory and the jdasma nutritive.] II. Fats (0-1 to 0-2 per cent.).—Neutral fats (tristearin, tripalmitin, triolein) occur in the blood in the form of small microscopic granules, which, after a meal ] ich in fat (or milk) render the serum quite milky. [The amount of fat in the serum of fasting animals is about 0'2 per cent.; during digestion 0-4 to 0-6 per cent; and in dogs fed on a diet rich in fat it may be 1-25 per cent. Tliere are also minute traces oi fatly acids (succinic). Riihrig showed that soluMc soaps, i.e., alkaline salt^ of the fatty acids, cannot exist in the blood. Cholesterin may be considered alono- with the fats. It occurs in considerable amount in nerve-tissues, and, like fats, is extracted by ether from the dry residue of blood-serum. Hoppe-Seyler found 0'019 to 0-314 per cent, in the serum of the blood of fattened geese. There is no fat in the red blood-corjaiscles. Lecithin (its de- composition-products, glycerin-phosphoric acid and protagon) occur in scrum and also in the blood-corpuscles.]
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