Part II.

Materia Medica.

By some, spring and winter wheat are considered only asvarieties, not as distinct species. The latter is the mostproductive, and is most commonly cultivated on that account;for there is no material difference in the grains they produce,which are indiscriminately employed for every purpose.

Wheat flour consists principally of gluten, starch, albumen,and a sweet mucilage. These may be separated by formino-the flour into a paste with a little water, and washing thispaste with fresh quantities of water until it runs from it co-lourless What remains is the gluten, which, if not the samewith, is very analogous to, the fibrine of animal substances.From the water with which the paste was washed, a whitepowder, Amylum, separates on standing. The albumen andsweet mucilage remain dissolved in the water. By evapora-ting it, the albumen first separates in white flakes, and thesweet mucilage may be got by total evaporation.

It is the presence of gluten which characterizes wheat flour;and on the due admixture of it-with the other constituents de-pends the superiority of wheat flour for baking bread

Bread is made by working the flour into paste with water,a quantity of some ferment, such as yeast, and a little muriateof soda to render it sapid, allowing the paste to stand until acertain degree of fermentation take place, and then baking itin an oven, heated to about 488°. During the fermentation,a quantity of gas is formed ; and as it is prevented from e-scapingby the toughness of the paste, and dilated by the heatof the oven, the bread is rendered light and spongy. In thisprocess the nature of the constituents of the flour is altered,for we are not able to obtain either gluten or starch frombread-

Medical use —Bread is not only one of the most importantarticles of nourishment, but is also employed in pharmacy formaking cataplasms, and giving form to more active articles.An infusion of toasted bread has a deep colour and pleasanttaste, and is an excellent drink in febrile diseases, and debili-ty of the stomach.

Amylum.

Starch —The general properties of starch have been alreadyenumerated. It is found in many vegetables combined withdifferent substances. Fourcroy, accordingly, makes variousspecies of it; as, combined,

1. With gluten or fibrine; as in wheat, rye, and othersimilar seeds.

2. With extractive; as in beans, peas, lupins, &c.