Page:Popular Science Monthly Volume 25.djvu/655

Rh differences, I suspect, are all due to the difficulty of isolating the substances in question, especially of the vegetable substance, which is so intimately mixed with the starch, etc., in its natural condition that complete separation is of questionable possibility.

This will be understood by the following description of the method of separation as given by Miller ("Elements of Chemistry," Vol. III): "Legumin is usually extracted from peas or from almonds, by digesting the pulp of the crushed seeds in warm water for two or three hours. The undissolved portion is strained off by means of linen, and the turbid liquid allowed to deposit the starch which it holds in suspension; it is then filtered and mixed with dilute acetic acid. A white flocculent precipitate is thus formed, which must be collected on a filter and washed."

This is but a mechanical process, and its liability to variation in result will be learned by anybody who will repeat it, or who has separated the gluten of flour by similar treatment.

Practically regarded in relation to our present subject, casein and legumin may be considered as the same. Their nutritive values are equal and exceptionally high, supposing they can be digested and assimilated. One is the most difficult of digestion of all the nutritive constituents of vegetable food, and the other enjoys the same distinction among those of animal food. Both primarily exist in a soluble form; both are rendered solid and insoluble in water by the action of acids; both are precipitated as a curd by rennet and both are rendered soluble after precipitation or are retained in their original soluble form by the action of alkalies. They nearly resemble in flavor, and John Chinaman makes actual cheese from peas and beans.

These facts, coupled with what I have already said concerning cheese and its cookery, will doubtless lead my readers to expect something concerning pease-pudding and potash in my next.

"Pease-pudding hot, pease-pudding cold, Pease-pudding in the pot, nine days old."

I leave to Mr. Clodd the historical problem of determining whether this notable couplet is of Semitic, Aryan, Neolithic, or Palæolithic origin. Regarded from my point of view it expresses a culinary and chemical principle of some importance, and indicates an ancient practice that is worthy of revival.

I have lately made some experiments on the ensilage of human food, whereby the cellular tissue of the vegetable may be gradually subjected to that breaking up of fiber described in No. 28. One of the curious achievements of chemical metamorphoses that is often quoted as a matter for wonderment is that of converting old rags into sugar by treating them with acid. The wonderment of this is diminished, and its interest increased, when we remember that the cellulose