COMMON WHEAT.

593

starch yields a mucilage, which, if sufficiently concentrated, forms a jelly[hydrate of starch) on cooling. With iodine, a cold decoction of wheatstarch forms the iodide of starch, the blue colour of which is removed byalkalies or heat.

The starch of some plants (e. g. the potatoe) is composed of concentricUyers (Fritzsche, Poggendorf's Ann. d. Phys Bd. xxxii. S. 129 ; also* ayen, quoted by Lindley, in his Introd. to Botany, 3d ed. p. 557).

Composition of Starch . —Starch has the following composition:—

Eq. Eq. Wt. Per cent. F. Marcet. Prout.

Carbon . 7 .. 42 ... 43*75 ... 43*7 ... 42*80

Hydrogen . 6 ... 6 ... 6*25 ... 6*7 ... 6*35

Oxygen. 6 ... 48 ... 50*00 ... 49*7 ... 50*85

Starch . 1 ... 96 ... 100*00 ... 100*1 ... 100*00

. Physiological Effects. —Wheat surpasses all other cereal grains inlls nutritive qualities, in consequence of containing more gluten. Ityields the finest, whitest, and most digestible kind of bread. Flour ise inployed in medicine to form emollient and demulcent preparations.

Wheat-starch, though highly nutritious, is not employed alone as an'irticle of food. Its taste is somewhat disagreeable, and it is moredifficult of digestion than other starchy substances.

Uses. —Wheat-flour is rarely used in medicine. It is occasionallyCrinkled over burnt or scalded parts, and is a constituent of someP (, »ltices, as Cataplasma fermenti , Ph . L. Mixed with water, so as to<)r m a thin mucilage, it may be employed as a chemical antidote in some? as cs of poisoning, as by the bichloride of mercury, sulphate of copper,° c * * 1 * * * ne, &c. It is used in pharmacy for enveloping pills.

Starch powder is used as a dusting powder to absorb acrid secretions

and

civ,

prevent excoriations. It is used as an emollient and demulcent

I’ster in inflammatory conditions of the large intestines, and as a vehicle" Jr fhe formation of other more active enemata. It is an antidote forscoffing by iodine, and is sometimes given in combination with this“stance to prevent its local action (vide p. 121). It enters into the^position of the Pulvis Tragacanthm compositus, Ph . L.

^ecoctum Amyli, L. Mucilago Amyli, E. D. — Decoction, orki\! U g e °f starc h- “ Take of starch, 5iv. (jiij. E. ; 5vj. D.); water, Oj.l in> »^ 16 ‘ starc ^ with the water gradually added, then boil for a shortIt is sometimes used alone, as an enema in dysentery, irritation

<jf th

e rectum, &c. It is a constituent of the Enema Opii, L.

iisgj P ANI s Triticeus. Wheaten Bread .— Crumb of bread (mica pants) is sometimesMis n! tbe formation of pills; but is objectionable for this purpose, on account of thethe r.„ us made becoming- excessively bard by keeping. Furthermore, in some cases,thl 9 ® 0,lst ituents of bread decompose the active ingredients of the pills. Thus tbe^<‘ 1 ( 1 - S0l H um °f bread decomposes and renders inert nitrate of silver. Crumb ofbep, ls most valuable for the preparation of poultices. The bread and water poultice isMi in • b y covering some crumb of bread in a basin with hot water : after it has stood forMclj pour off the excess of water, and spread the bread about one-third of an inch

Med I!" S °l t Pnen, and apply to the affected part. Sometimes lint dipped in oil is ap-' l . t Go i' nea ! t l’ *l |e poultice (Abernethy, Lancet, v. 5, 1824, p. 135). Decoction of poppy,

l >o n a /? >s water > may be substituted for common water. This is a valuable applica-

ble J?, gmonous inflammation. A bread and milk poultice, to which lard is some-

dded, is also used to promote suppuration ; but it should be frequently renewed,

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