Outlines of practical physiology : being a manual for the physiological laboratory, including chemical and experimental physiology, with reference to practical medicine / by William Stirling.

  • William Stirling
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of practical physiology : being a manual for the physiological laboratory, including chemical and experimental physiology, with reference to practical medicine / by William Stirling. Source: Wellcome Collection.

    42/690 (page 12)
    thermometer, provided with a long narrow bulb. The solution of the pro- teid, of which the temperature of coagulation is to be determined, is placed in the test-tube, the quantity being just sufficient to cover the thermometer bulb. The whole apparatus is then gradually heated, and the experimenter notes the temperature at which the liquid first shows signs of opalescence” (Gamgee). 6. Circumstances modifying coagulating tem¬ perature.—Place 5 c. c. of solution of albumin in each of three test-tubes, colour with neutral solution of litmus, and label A, B, C. To A add a drop of very dilute acetic acid (o'l p.c. diluted five or six times); to B a very dilute solution of NaHO (on p.c. similarly diluted); C is neutral for comparison. Place all three tubes in a beaker with water and heat gradually. Coagulation occurs first in A, next in C, and not at all in B, the alkaline solution. Use thermometer. 7. Influence of salts on coagulation.—To blood- serum diluted one-fifth add an equal volume of saturated solution of NaCl. Divide into two por¬ tions. Boil one portion = coagulation ; acidify the other with acetic acid ; it may become slightlv turbid, and on heating it coagulates. The more salts present in an albuminous solution the less is the coagulation temperature dependent on the re¬ action of the fluid. The less the amount of salts the nearer neutral—or even slightly acid—must the reaction be to ensure coagulation. 8. Crystallisation of proteids — e.g., Egg-albu¬ min.—Various methods are employed, but the most convenient is that of Hopkins and Pinkus,* which is a modification of the original method by Hof- meister [1891]. Fresh egg-white is thoroughly mixed with an equal bulk of saturated neutral filtered solution of Am.2S04, the latter being gradually added—10 c.c. to 15 c.c. at a time—and the mixture stirred with an egg-whisk after each addition. The mixture is strongly alkaline and smells of ammonia. Let the well-whisked mixture stand overnight, filter, and to the clear filtrate add from a burette very cautiously more Am.2S04 until a permanent precipitate is obtained. Add a few drops of distilled water until the solu¬ tion is again clear. Drop in from a burette 10 p.c. acetic acid until a distinct and bulky precipitate is obtained. Cork the bottle, and let it stand for 24 hours, when abundance of small rosettes or fan-shaped aggre¬ gations of microscopic needle-shaped crystals are obtained when a prepara¬ tion is examined with ^-inch objective. On adding the Am2S04 to the proteid, ammonia is evolved, and this free alkali interferes with the separation of crystals, hence the addition of acetic acid. Pure egg-albumen, crystals of serum-albumin (Gurber), and allied bodies have thus been ob¬ tained in large quantities.t If a dye be added during crystallisation the crystals are correspondingly coloured. Tig. 1.—Apparatus for de¬ termining the Coagulation Temperature of Proteids. *Journ. of Phys., xxiii., 132, 1898. + Journ. of Phys., xxv., 306, 1900.