CLASS V. Coagulated proteids.—Insoluble in Water, dilute acids and alkalies, and in neutral saline solutions of all strengths; soluble only in strong acids and- strong alkalies, except at high temperatures, when dilute preparations will effect a slight solu tion. The coagulated proteids are produced by heating to 158' Fahr. solutions of egg-albu men or serum-albumen, or acid or alkali-albumens, or fibriue suspended in water. At the temperature of the body they are converted by the action of the gastric juice, or of pancreatic juice in an alkaline medium, into peptones. This action takes place during. the digestion of cooked meats.
CLAss VI. remarkable organic compounds are very soluble in water, and are not precipitated from their aqueous solutions by acids or alkalies or by boiling. They are insoluble in alcohol, but are also with difficulty precipitated by it, and when precipitated are unchanged by the process. They are not precipitated by sul phate of copper, chloride of iron, nor (with some exceptions) by ferro-cyanide of potassium or acetic acid. In these respects they differ f rom most other proteids. Precipitation is, how
ever, produced by chlorine, iodine, corrosive sublimate, nitrate of merr-ury, nitrate of silver, acetate of lead, and tannin. Liken]] proteids, the peptones have a specific left-hand rotatory power over polarized light ; but unlike the others, boiling produces no change in the amount of rotation. Peptones are, doubtless, formed in large quantities in the stomach and intestines during digestion; but only a small quantity can be found in the digesting mass or in the chyle. 1Vithout attempting to settle the question as to where the final conversion of proteids into peptones takes place (perhaps upon the sur face of the mucous membrane of the stomach, which is probable), it may be remarked that it is generally conceded that the peptones are absorbed very soon after they are formed. See lln:EsTios,