The Chemistry of Cookery

very slow evaporation, I find that it still contains some of its acquired water, and that I cannot drive away this newly-acquired water without destroying some of its characteristic properties—its solubility and gluey character. Before returning to its original weight as crude isinglass, it becomes somewhat carbonised. Hence, I infer that the cookery of gelatin consists in converting the original membrane more or less completely into a hydrate of its former self. According to this, the ‘prepared gelatin’ sold in the shops is hydrated gelatin, completely hydrated, seeing that it is completely and readily soluble. The membranes of our ordinary cooked meat are, if I am right, partially hydrated, in varying degrees, and thereby prepared for solution in the course of digestion. The varying degrees are illustrated by the differences in a knuckle of veal or a calf’s head, according to the length of time during which it has been stewed, _i.e._ subjected to the hydrating process. The second stage of the cookery of gelatin is the solution of this hydrate, as in soups, &c. Carpenters’ glue is crude hydrated gelatin, made by stewing or hydrating hoofs of horses, cattle, &c., or the waste cuttings of hides. The carpenter knows that if he allows his solution of glue to boil (such a solution boils at a higher temperature than pure water), it loses its tenacity, becomes cindery, or, as I should say, dehydrated or dissociated, without returning to the original condition of the organised membranes. Even a frequent reheating at the glue-pot temperature ‘weakens’ the glue, and therefore he prefers fresh glue, and puts but a little at a time into his glue-pot. The applications of this theory will appear as I proceed. A sheep or an ox, a fowl or a rabbit, is made up, like ourselves, of organic structures and blood, the organs continually wasting as they work, and being renewed by the blood; or, otherwise described, the component molecules of these organs are continually dying of old age as their work is done, and replaced by new-born successors generated by the blood. These molecules are, for the