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.

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    Cut it into small pieces, add cold water. The gelatin swells up by imbibition of water, but does not dissolve. Heat, the gelatin dissolves. Allow it to cool; it gelatinises if the solution is strong enough. (A) General proteid tests for gelatin. (а) Xanthoproteic test.—Add HNOs and boil = a light yellow colour with no previous precipitate ; the fluid becomes lemon- coloured on adding ammonia. This reaction is feeble, owing to the absence of the phenol group, C6H5OH. (б) Millon’s reagent = no pinkish-red precipitate on boiling, due to the absence of the tyrosin nucleus. This reaction may be obtained with commercial gelatin, but not with pure gelatin. (c) Piotrowski’s test = a blue-violet, rather than a violet colour, with NaHO and CuS04 (resembling somewhat proteids). (d) Not precipitated by acetic acid and potassium ferrocyanide (unlike albumin, but like peptone). (e) Not coagulated by heat (unlike albumin). (/) Not coagulated by boiling with Na2S04 and acetic acid (unlike albumin). (g) Precipitated by saturation with MgS04 or (NH4)2S04. (B) Special reactions for gelatin. (h) It is not precipitated by acetic acid (unlike mucin) or alkalies. (i) Mercuric chloride = no precipitate (unlike albumose and peptone). (j ) Lead acetate = no precipitate (unlike proteids). The heavy metals do not precipitate it (unlike proteids). (k) Tannic acid = white precipitate, insoluble in excess. (l) Picric acid (sat. sol.) = yellowish-white precipitate, which disappears on heating and reappears on cooling. (■m) It is precipitated by alcohol, and also by platinic chloride. II. Chondrin is obtained by the prolonged boiling of hyaline cartilage, which largely consists of the substance “ Chondrigen.” Preparation.—Boil costal cartilages (perichondrium removed) several hours in water = opalescent fluid, which gelatinises on cooling. (a) Acetic acid = white precipitate, soluble in great excess. (b) Dilute mineral acids = white precipitate, readily soluble in excess. (c) Not precipitated by acetic acid and potassium ferrocyanide. III. Mucin, see “ Saliva.” It is also found in the ground substance of connective tissue and tendon. There are probably
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