Elements of human physiology.

  • Henry Power
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology. 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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    40° C. in dilute HCl it dissolves, and the solution contains acid-albumin. Class VI.—CoagXllated proteids.—Insoluble in water, dilute acids, and alkalies. Gives Millon's reaction. Are dissolved when digested at 35° C. to 40° C. in artificial gastric or pancreatic juice, giving rise to peptones. Class VII.—Liardaceia or amyloid substance.— Insoluble in water, in dilute acids, in alkaline carbonates; not dissolved by gastric juice at the temperature of the body, coloured brownish-red or violet by iodine. Oeneral characters of the proteids.—All the com- pounds included in this group of substances contain nitro- gen and sulphur, and their chemical composition is ex- pressed by a fomiula more or less closely resembling the following: Cg4ll7]Sr;^g022S4. They are amorphous, with variable solubility in water and acids; usually soluble in alkalies; almost insoluble in alcohol and ether. The aqueous solutions are neutral. They are not volatile ; they burn with an odour of burnt feathers, giving off ammo- niacal fumes, and leaving a residue of ash which chiefly consists of lime phosphate. Exposed to the air they easily undergo decomposition. Calcined with potash, or boiled with sulphuric acid, they yield leucin and tj-rosin. Hot concentrated nitric acid converts them into a yellow body, xanthoproteic acid. Treated with acids or with alkalies, or when allowed to undergo putrefactive decomposition, they give, amongst others, the following products of de- composition : Volatile fatty acids; oxalic, acetic, formic valerianic, fumaric, and asparagic acids; leucin, tyrosin, and ammonia. When treated with oxydising agents, they yield formic, acetic, propionic, butyric, valerianic, capric, and benzoic acids ; the aldehydes of these acids and volatile organic bases, aceto-nitril, valero-nitril, and propio-nitril. They rotate polarised light to the left. They are pre- cipitated from their solutions by an excess of the strong mineral acids, by acetic or hydrochloric acid, and po- tassium ferrocyanide, the basic acetate of lead, mercury bichloride, tannin, and by potash carbonate in powder. Tests for the proteids. 1. Kitric acid test:—Heat the liquid, and add nitric acid till the reaction is strongly acid : a precipitate falls which undergoes no change on the addition of acid, 2. Sodium sulphate test.—Add acetic acid till the reaction is strongly acid. Mix with an equal volume of concen- trated solution of sodium sulphate, and boil; the proteids are precipitated.