37. Triticum vulgare, Kunth.—Common Wheat.

Sex. Syst. Triandria, Digynia.
(Farina; farina seminis: Amylum; seminis, faecula, L.: Amylum; fecula of the seeds, E.: The seeds, from which are prepared flour and starch, D.)

History.—In the earlier ages wheat was an esteemed article of food [Levit. ii.], and is frequently spoken of by Hippocrates [De victus rat. lib. iii. p. 374, ed. Foesii.], who calls it πυρός, and mentions three kinds of it: wheat, simply so called, three-month wheat, and Sitanian wheat. Pliny [Hist. Nat. xviii. 12.] describes several kinds of triticum.

Botany. Gen. Char.—Spikelets three or many flowered: the fructiferous rachis generally articulated, flowers distichous. Glumes two, nearly opposite, almost equal, awnless or awned: the upper one bicarinate; the keels more or less aculeato-ciliate. Stamina three. Ovarium pyriform, hairy at the apex. Stigmata two, terminal, subsessile, feathery; with long, simple, finely-toothed hairs. Scales two, generally entire and ciliated. Caryopsis externally convex, internally concave, and marked by a deep furrow, distinct, or adhering to the paleae (Kunth).

Sp. Char.—Spike four-cornered, imbricated; with a tough rachis. Spikelets generally four-flowered. Glumes ventricose, ovate, truncate, mucronate, compressed below the apex, round, and convex at the back, with a prominent nerve. Flowers awned or awnless. Grains loose (Kunth).

α. aestivum [The distinction of wheats into summer and winter wheats, or into those sown in the spring and those sown in the autumn, has been objected to on the ground that under the name of T. hybernum are included several of the earlier sorts of spring wheat, and under T. aestivum, are included several wheats which require as long a time to arrive at maturity as the common winter sorts.], Kunth; T. aestivum, Linn. D.; Spring or Summer Wheat.—Annual; glumes awned.—This variety includes a great many sorts known to farmers by different names, and which may be arranged in two divisions—viz., the white bearded and the red bearded.
β hybernum, Kunth; T. hybernum, Linn.; T. compactum, Host.; T. velutinum, Schuebl.; T. erinaceum, Hort. Hal.; Winter Wheat.—Biennial; glumes almost awnless. This variety also includes many sorts, which maybe arranged in two divisions—viz., the white beardless and the red beardless.—Talavera wheat is a white beardless winter wheat. Mr. Hard, miller, of Dartford, tells me that "this kind (Talavera wheat) is far superior to any description of wheat, either foreign or English; and the great advantage it possesses consists in its strength, colour, and sweetness. The reason of there being so small a quantity at market, arises from the fact of its being so unprofitable to the farmer, scarcely producing one crop in three, which I greatly regret, as it is the most valuable grain we have; and, technically speaking, if the flour is properly manufactured, 8 oz. will absorb as much liquor as 11 oz. of that used by the baker."

Hab.—It is a native of the country of the Baschkirs, and is cultivated in Europe.

Besides T. vulgare, other species of Triticum are cultivated. The following are the chief:—
T. turgidum, Kunth; Turgid Wheat. Some of the sorts of this species have smooth ears; others downy, woolly, or velvety ears.—This species includes the T. turgidum, Linn. and T. compositum, Linn.
T. durum, Kunth; Hard or Horny Wheat.
T. polonicum, Kunth; Polish Wheat.
T. Spelta, Kunth; Spelt Wheat.
T. monococcum, Kunth; One-grained Wheat.

Description.—Wheat-grains (caryopsides tritici; semina tritici), as brought to market, are completely devoid of their paleae (chaff or husk).

The number of parts into which millers separate wheat varies in different localities. According to Mr. Hard, miller, of Dartford, in Kent, the products obtained by grinding one quarter or eight bushels of wheat are as follows:—

Produce of one quarter of Wheat weighing 504 lbs.

Wheat-grains vary in size, smoothness, transparency, and hardness, and in the thickness of their integuments; and, consequently, the relative proportions of bran (and pollard) and flour which they yield vary. The integument readily separates in soft-grained wheat, but with difficulty in the hard-grained: the former, therefore, yields more bran and less flour; while the latter produces flour of a lower quality, because it is intermixed with some of the ground integuments.

Semolina, Soujee, and Manna Croup [The term Manna Croup is probably derived from Manna-Grout, the name of a nutritious food prepared from the grain of Glyceria fruitans. (See Curtis, Fl. Lond. vol. i. pl. 7; also, Tooke's View of the Russian Empire, vol. iii. p. 168, 2d ed. 1800.] are granular preparations of wheat, deprived of bran.

I am indebted to Mr. Hard for the following notice (as well as for samples) of the products obtained in grinding wheat:—

"The wheat having been ground in the usual way, should be allowed to remain in the meal for some time before dressing, which removes the heat caused by the process, and enables the miller to obtain more flour, and the baker a better quality, than if dressed immediately it is ground.

"The process of dressing is by a wire cylinder containing a certain number of sheets of different texture or fineness, which cylinder contains eight hair-brushes attached to a spindle passed through the centre of the cylinder, and laid out so as to gently touch the wire: this cylinder is fed by a shoe with the meal; then the flour and offal, after passing through the wire in this way, are divided by wood partitions fixed close to the outside of the cylinder. The produce of wheat-meal dressed through the wire machine consists of—1st, Flour; 2d, White Stuff, or Boxings, or Sharps; 3d, Fine Pollard; 4th, Coarse Pollard, or Horse Pollard; 5th, Bran. The second product (i. e. the White Stuff) is then submitted to another dressing through a fine cloth machine, and produces 1st, Fine Middlings, for biscuits; 2d, Toppings or Specks; 3d, Dustings; 4th, Best Pollard, Turkey Middlings or Coarse Middlings.

Composition.—1. Wheat-flour has been analyzed by Vogel [Quoted by L. Gmelin, Handb. d. Chem. Bd. ii. S. 1341.], by Proust [Ann. Chim. Phys. t. v. p. 340.], by Henry [Journ. de Pharm. t. viii. p. 51, 1822; and t. xv. p. 127, 1829.], and by Vauquelin [Ibid., t. viii. p. 353, 1822.]. The following are the results obtained by Vauquelin.

Composition of Wheat Flour.

Payen's analysis of wheat has been already given (see ante, p. 106); as also the proportions of water, proteine matters, and starch, according to the investigations of Horsford and Krocker (see vol. i. p. 116); and the composition of the ash of wheat (see ante, p. 106).

Mr. Johnson [Lectures on Agricultural Chemistry, 2d edit. p. 867.] found that in 20 samples of English flour the proportion of water varied from 15 to 17 per cent.

The proportion of the organic constituents of wheat is liable to considerable variation, according to soil, climate, variety of seed, mode of culture, time of cutting, and quality of manure.

2. The composition of bran, like that of wheat-flour, is subject to great variation, but the following is given by Mr. Johnston as the average:—

1. Starch.—As wheat-starch is an article of the materia medica, it will be noticed among the official preparations (see ante, p. 124).
2. Proteine Matters.—The quality of proteine matters in wheat has been already stated (see vol. i. p. 116, and vol. ii. p. 123). Wheat contains at least four different proteine compounds, namely, albumen, vegetable fibrine, gluten, and caseine. They have an analogous composition, and contain each about 16 per cent. of nitrogen.
If wheaten-dough be washed on a sieve by a stream of water, a milky liquid passed through, and a tenacious elastic mass is left behind called crude gluten, or sometimes Beccaria's gluten. The milky liquid holds in solution gum, sugar, and albumen; and in suspension starch: the crude gluten contains vegetable fibrine, gluten, caseine, or mucine, and oil. According to Saussure [Bibliotheque universelle, Sciences et Arts, t. liii. p. 260, 1833.] crude gluten has the following composition:—

α. Vegetable Albumen.—Obtained by allowing the milky liquid above mentioned to deposit its starch, and then heating the supernatant liquor nearly to boiling: flakes of coagulated albumen are formed. Its composition was found by Dr. Bence Jones [Liebig's Animal Chemistry.]to be carbon 55.01, hydrogen 7.23, nitrogen 15.92, oxygen, sulphur, and phosphorus 21.84.
β. Glutin; Gliadine (from γλία, glue); Pure Gluten.—Obtained by boiling crude gluten in alcohol, which extracts glutin, caseine or mucine, and oil. By cooling, the caseine is deposited. The supernatant liquid is then evaporated to dryness, and the adhesive mass thus obtained digested with ether to extract the oil: the residue is glutin. Its composition has been before noticed (see vol. i. p. 112).
γ. Vegetable Fibrine; Zymome (from ζύμη, ferment).—This is the part of crude gluten which is insoluble in alcohol. Mulder considers it to be coagulated albumen; Liebig as vegetable fibrine. Johnston, on the other hand, thinks it different from both albumen and fibrine, and, therefore, calls it simply gluten. When obtained as above described it much resembles the fibre of lean beef. Dr. Bence Jones ascertained its composition to be carbon 55.22, hydrogen 7.42, nitrogen 15.98, oxygen, &c., 21.38.
δ. Caseine.—After the albumen has been separated by heat from the aqueous liquid before alluded to, the addition of acetic acid causes the separation of what is supposed to be caseine. The white flocculent substance, which deposits on cooling from the alcoholic liquor in which crude gluten has been boiled, and which has been called mucine, somewhat resembles caseine.
3. Oil.—Obtained by digesting wheat flour in ether. The quantity procured varies from 1 ½ to 3 per cent. As bran yields about twice as much as fine flour, it follows that the oil exists in greater proportion in the outer than in the inner part of the grain. The oil resembles the fatty oils or butter in its properties. By washing wheat-dough, part of the oil is washed out, and part remains in the crude gluten.
4. Water.—According to Johnstone, English flour contains, on an average, from 15 to 17 per cent. of water.
5. Mineral Constituents.—The composition of the ashes of wheat has been already stated (see ante, p. 106). The most important of these constituents are the alkaline and earthy phosphates.

Chemical Characteristics.—The cold decoction of wheat-flour forms, with tincture of iodine, the blue iodide of starch. Nitric acid gives wheat-flour a fine orange-yellow colour. Recently-prepared tincture of guaiacum forms a blue colour with good wheat-flour.

Diseases of Wheat. [For an excellent account of the diseases of wheat, see the Rev. Professor Henslow's Report on this subject, in the Journal of the Royal Agricultural Society of England, 1841, vol. ii. part 1.]—Five diseases of wheat are produced by the attacks of parasitic fungi; namely, 1st, bunt, smut-balls or pepper-brand, produced by Uredo Caries, De Candolle; 2dly, smut, dust-brand, or burnt-ear, produced by Uredo segetum; 3dly, rust, red-rag, red-robin, or red-gum, caused, as Professor Henslow has shown, by the young state of Puccinia graminis, which was formerly supposed to form two distinct fungi, to which the names of Uredo Rubigo and U. linearis had been given; 4thly, mildew, produced by the Puccinia graminis in a more advanced period of its growth; and 5thly, ergot, caused by the Oidium abortifaciens (see ante, p. 87).

Two diseases of wheat are produced by parasitic animalcules; namely, first, the ear-cockle, purples, or peppercorn, caused by a microscopic, eel-shaped animalcule, called Vibrio Tritici; and, secondly, the wheat-midge, an abortion of the grain caused by a minute two-winged fly called Cecidomyia Tritici.

Corn affected with any of these diseases is of course deteriorated in value; but we have still to learn what are the precise effects on the animal economy of grain thus infected. The bunt imparts to flour its disgusting odour, and makes it less fit for bread; but flour thus tainted is used in the manufacture of ginger-bread. Smut does not give any unpleasant odour to corn, which, when infected with it, is frequently used for feeding fowls, apparently without producing any ill effects. I have ascertained that ergot of wheat is as powerful in its action on the uterus as ergot of rye. It has been suggested that some remarkable cases of spontaneous gangrene which occurred at Wattisham, in Suffolk, in 1762, may possibly have arisen from the presence of ergot in the corn used by the persons affected; but of this there is no evidence.

Deterioration; Adulteration.—By exposure to a damp air, wheat-flour absorbs moisture, and, after some time, acquires a musty odour, and becomes mouldy; the gluten being the first to suffer change. In this state it may be readily conceived that wheat-flour would prove injurious to health.

Wheat-flour is subject to adulteration with various vegetable and mineral substances.

Among vegetable substances used for the purpose of adulterating wheat-flour, the following have been named: potato starch, the meal of other cereal grains (viz., of maize, rice, barley, and rye), of buckwheat, and of certain leguminous seeds (viz., of beans, peas, and vetch).

In the detection of these adulterations, the microscope lends important assistance. It enables us to judge of the size and shape, the markings on, and the isolation and agglomeration of, the starch grains, and thereby to distinguish the starch grains of one meal from those of another.

In some cases, the microscopic examination of suspected flour is aided by the use of a solution of potash. Thus it enables us readily to detect the presence of either potato starch or the meal of leguminous seeds. If a solution containing about 1 ¾ per cent. of potash [I find that a mixture of 1 measure of liquor potassae, Ph. L., and 2 or 3 measures of distilled water, readily distinguishes potat-starch from wheat-starch.] be added to a mixture of potato-starch and wheat-starch (or wheat-flour), the granules of potato-starch swell up, and acquire three or four times their original volume, while those of wheat-starch are scarcely affected by it. A solution of potash, containing about 12 per cent, of potash, dissolves all the varieties of starch, but not cellulose; hence, if to wheat-flour, intermixed with the meal of some leguminous seed, this solution be added, the starch grains dissolve, and the hexagonal tissue of the adulterating leguminous seed is rendered very obvious [Donny, Ann. de Chim. et de Phys. 3me Sér. t. xxi. p. 5, 1847; and Journ. de Pharm. et de Chim. 3me. Sér. t. xiii. p. 139, 1848. Also Mareska, Journ. de Pharm. et de Chim. 3me Sér. t. xii. p. 98, 1847; also, Pharmaceutical Journal, vol. vii. p. 394, 1848.].

Occasionally, polarized light may be used to aid the microscope in detecting adulterations of wheat-flour. Thus, unlike wheat-starch, the starch of the oat produces no effect on polarized light, and presents no crosses when viewed by it.

In the detection of the meal of the leguminous seeds, the odour and flavour of the suspected flour, and its chemical characters, aid in detecting the fraud. If the suspected flour be digested with twice its volume of cold water, the infusion filtered and a few drops of acetic acid added to it, a precipitate of legumine (a kind of caseine) is produced, if the meal of a leguminous seed be present [Journ. de Pharm. et de Chim. 3me Sér. t. xi. p. 322, 1847; also, Pharmaceutical Journal, vol. vii. p. 84, 1847.]; but wheat-flour, treated in the same way, yields a slight precipitate (of caseine), and, therefore, this test must not be relied on. Donny has pointed out a mode of detecting the meal of two leguminous seeds, viz., the vetch (Vicia sativa), and beans (Faba vulgaris, common tick bean): it consists in exposing the suspected flour to the successive action of the vapours of nitric acid and ammonia: wheat-flour, when thus treated, becomes yellow; but the meals of the leguminous seeds just referred to become red, and hence, wheat-flour adulterated with either of them becomes more or less spotted with red, according to the proportion of the leguminous meal present.

The mineral substances which have been used to adulterate wheat-flour are chiefly chalk and sulphate of lime (plaster of Paris). White clay and bone-ashes are also said to have been used. Sulphate of copper and alum are sometimes added to bad wheat-flour to improve its quality and render it more fitted for making bread. These different adulterations may be readily detected. Their quantity and nature may be judged of by incinerating the suspected flour, weighing the ash (which in genuine flour amounts to about 1 or 1 ¼ per cent.), and determining its nature. Flour mixed with chalk effervesces on the addition of hydrochloric acid, and yields a calcareous solution detectable by a solution of oxalatc of ammonia (see vol. i. p. 568). Flour mixed with sulphate of lime, when digested in water, yields a solution which answers to the tests both for lime (see vol. i. p. 568) and for sulphuric acid (see vol. i. p. 368). Pure wheat-flour is almost completely soluble in a strong solution of potash containing about 12 per cent. of alkali; but mineral substances used for the purpose of adulteration remain undissolved.

Physiological Effects.—The nutritive qualities of wheat are similar to those of the cereal grains generally, and which have been already noticed (see ante, p. 107).

As it exceeds other kinds of corn in the proportion of proteine matters which it contains, so it surpasses them in its flesh- and blood-making qualities. But, as it contains less starch and fatty matters than some other cereal grains, it is probably inferior to the latter as a fattening agent.

The different parts of the grain differ in composition, and, therefore, in nutritive value. The external sub-epidermoid part contains a larger proportion of oil, of salts (chiefly phosphates), and albuminous and caseine matter than the more internal and farinaceous portion; and it is, therefore, probable that the finest flour, which has been freed as much as possible from all traces of bran, is actually somewhat less nutritive than the coarser flour.

Wheat-flour, especially when baked, is rather constipating than purgative. In this it differs from both barley-meal and oat-meal. Infants who are fed on baked flour frequently suffer with constipation; and to relieve this it is sometimes found necessary to substitute a portion of barley-meal for an equivalent weight of wheat-flour.

Wheat-flour yields the finest, whitest, lightest, and most digestible kind of bread. It owes its superiority in these respects to the large quantity of tenacious gluten which it contains.

Undressed wheat-flour appears to act, by the bran which it contains, as a mechanical stimulant to the bowels; and hence brown bread is resorted to for the purpose of counteracting habitual constipation.

Uses.—Wheat-flour is employed in medicine both as a therapeutical and a pharmaceutical agent. It is used with great advantage as a dusting powder in burns and scalds. It cools the part, excludes the air, and absorbs the discharge, with which it forms a crust which effectually protects the subjacent part. When the crust has become detached by the accumulation of purulent matter beneath, a poultice may be applied, and, after the removal of the crust, the exposed surface may be again dusted over with flour.

A mixture of flour and water is used as a chemical antidote in poisoning by the salts of mercury, copper, zinc, silver, and tin, and by iodine (see vol. i. p. 203).

Flour is a constituent of some poultices, as the yeast-poultice (see ante, p. 86), and the mustard-poultice.

It is used in pharmacy for enveloping pills.

1. AMYLUM TRITICI; Amylum; Wheat-Starch.—This starch was known to Pliny [Hist. Nat. lib. xviii. cap. 17, ed. Valp.] , who says the discovery of it was first made in Chios, and that it received its name amylum (άμυλον; from α, negative, and μύλος, a mill) because it was not prepared by grinding in a mill.

There are various modes of preparing it, but the method followed in this country is a mechanico-chemical one, the starch being separated from the other ingredients of wheat, partly by mechanical agency, and partly by chemical means. The cellulose or woody fibre of the grain is separated by mechanical means; the gum, sugar, albumen, and soluble salts, are dissolved out by cold water; and the gluten is got rid of partly by allowing it to undergo decomposition, and partly by solution in the acetic acid which is developed by fermentation.

A mixture of coarsely-grained wheat is steeped in water in a vat for one or two weeks (according to the state of the weather), by which acetous fermentation is established. The acid liquor (called sour water, or simply sours) is drawn off, and the impure starch washed on sieves to separate the bran. What passes through is received in shallow vessels termed frames. Here the starch is deposited. The sour liquor is again drawn off, and the slimes removed from the surface of the starch, which is to be again washed, strained, and allowed to deposit. The liquid which is drawn off is called green water. If the operation of washing be again resorted to, the part washed off is called white water instead of slimes, the liquid itself being still termed green water. When, by these processes, the starch has become sufficiently pure, it is boxed; that is, it is placed in wooden boxes perforated with holes and lined with canvas, where it drains. It is then cut in square lumps, placed on chalk stones or bricks, to absorb the moisture, and dried in a stove. By this process the blocks are crusted (see ante, p. 108). The blocks are then scraped, papered, labelled, stamped, and returned to the stove. Here they split into columnar masses (like grain, tin, or basaltic columns), commonly called the race.

In commerce, there are two kinds of wheat-starch—one white, the other blue..

1. White wheat-starch is the sort which should be employed for dietetical or medicinal purposes. What is sold under the names of French starch and patent white starch is of this kind.

2. Blue wheat-starch is used by the laundress for stiffening linen. It owes its colour to finely-powdered smalt or indigo, which has been introduced into it before the boxing process. The Poland and glaze starches of the shops are of this kind. They are not adapted for medicinal purposes.

When examined by the microscope, wheat-starch is perceived to consist principally of large and small grains, with but few of intermediate size [The following measurements of the starch grains fo different sizes of common and spelt wheat were made by Mr. George Jackson:--Common Wheat. 1. .0009 of an English inch. 2. .0006. 3. .0004. 4. .0003. 5. .0002. 6. .0001. Spelt Wheat. 1. .0012 of an English inch. 2. .0010. 3. .0005. 4. .0003. 5. .0001.]. The smaller particles appear to be spheroidal or nearly so. The large ones are rounded, and flattened or lenticular. When at rest, they appear to be globular; but, by making them roll over in water, they are seen to be flattened, compressed, or lenticular; one of the flattened faces being sometimes a little more convex than the other. Viewed edgeways, the particles are strongly shaded. In the middle, or nearly so, of the flattened surface is the rounded, elongated, or slit hilum. This is surrounded by concentric rings, which extend frequently to the edge of the grains. When heated, the particles crack at the edges.

When heated in a tray in an oven to 300° F., wheat-starch acquires a buff colour, and is converted into dextrine or British gum.

Boiled in water, wheat-starch yields a mucilage, which, when sufficiently concentrated, forms, on cooling, a jelly (hydrate of starch). The consistence of this jelly is due to the mutual adhesion of the swollen hydrated integuments of the starch grains. When submitted to prolonged ebullition in a large quantity of water, the granule almost entirely dissolves, and the decoction, on cooling, does not gelatinize. With iodine the decoction, when cold, forms the blue iodide of starch, the colour of which is destroyed by alkalies and by heat.

The composition of wheat-starch is C₁₂H₁₀O₁₀.

Wheat-starch is not employed alone as food. As found in commerce, its taste is somewhat disagreeable.

Starch powder is used as a dusting powder to absorb acrid secretions and to prevent excoriation. Its decoction is used as an emollient and demulcent clyster in inflammatory conditions of the large intestines, and as a vehicle for the formation of other more active enemata. Starch is an antidote for poisoning by iodine, and is sometimes given in combination with this substance to prevent its local action (see vol. i. p. 405). It enters into the composition of the Pulvis Tragacanthae compositus, Ph. L.

2. DECOCTOI AMYLI, L. Mucilago Amyli, E. D.; Decoction or Mucilage of Starch.—(Starch ʒiv; Water Oj [Oss, D.].) Rub the starch with the water gradually added, then boil for a short time.)—It is sometimes used alone as an enema in dysentery, irritation of the rectum, &c. It is a constituent of the Enema Opii, L.

3. FURFURES TRITICI; Bran.—Decoction or infusion of bran is sometimes employed as an emollient foot-bath. It is also taken internally as a demulcent in catarrhal affections. Its continued use causes a relaxed condition of bowels. Bran poultices are applied warm in abdominal inflammation, spasms, &c. Bran bread is used in diabetes (see p. 127, foot-note).

4. FARINA TRITICI TOSTA; Baked Flour.—Wheat-flour lightly baked, so as to acquire a pale buff tint, is an excellent food for infants, invalids, and convalescents. Unlike the more amylaceous substances (such as arrow-root, tapioca, sago, &c.), it contains flesh- and blood-making as well as fat-making ingredients. Moreover, it has no tendency to relax the bowels; on the contrary, I think it is somewhat constipating. Hence, therefore, it may be used with advantage where there is a tendency to diarrhoea. When employed as an infant's food, it may be sometimes desirable to mix it with a fourth of its weight of prepared barley-meal, to obviate its constipating effects. It is prepared by boiling it in milk or milk and water, and is taken as a kind of pottage or gruel.

Hard's Farinaceous Food is a fine wheat-flour, which has been subjected to some heating process. It is an excellent preparation.

5. TURUNDAE ITALICAE; Macaroni, Vermicelli, and Italian or Cagliari Paste (in the form of stars, lentils, &c.).—These are pastes made with the finest and most glutinous wheat. By the artificial addition of wheat-gluten to the ordinary wheat, products may be obtained which rival the finest Italian pastes [Payen, Précis de Chimie Industr. p. 397, 1849.]. The granulated gluten (gluten granulé) of MM. Véron frères is a paste made in this way. These various preparations are agreeable and most nourishing foods. Boiled in beef-tea, or similar fluids, they may be taken with great advantage by invalids and convalescents.

6. PANIS TRITICEUS, L.; Wheaten Bread.—This is of two kinds, fermented or leavened, and unfermented or unleavened.

α. Panis fermentatus; Fermented or Leavened Bread.—The ingredients used in its manufacture are wheat-flour, salt, water, and yeast. In making the ordinary loaf-bread of London, the baker always employs a portion of potatoes; not for adulteration, but to assist fermentation, and to render the bread lighter. Patent yeast (see ante, p. 85) is generally employed by him on the score of economy. The yeast excites the fermentation of the sugar, which it converts into alcohol and carbonic acid: the former is dissipated in the oven, and the latter, distending the dough, causes it to rise, and gives the vesicular character to bread. During the process, a portion of starch is converted into soluble gum (dextrine) and a small portion of sugar.

The following table represents the comparative composition of the flour and bread of wheat, according to Vogel:--[Quoted by Gmelin, Handb. d. Chem. Bd.ii. S. 1341 and 1343; also, Journ. de Pharm. t. iii. p. 211, 1817.]

Flour in baking takes up a considerable quantity of water, the absolute amount of which, however, depends on several circumstances. Home-made bread baked in separate tins contains about 44 per cent. of water, whereas the flour from which it is made contains only about 16 per cent. Ordinary bakers' bread, baked in united loaves, contains as much as 50 or 51 per cent, of water. Various additions made to wheat-flour enable it to take up more water. Common salt does this: in the language of the baker it gives stiffness or strength to the dough. Alum (used by bakers under the name of "stuff") has a similar effect: it also augments the whiteness and fineness of bread, and renders it less liable to crumble. It, therefore,enables the baker to use an inferior flour with less chance of detection. Sulphate of copper (in the proportion of one grain to two pounds of flour) has a like effect, and has been used in some parts of Belgium to adulterate bread. It is said to enable the latter to take up 6 per cent. more water without appearing moister [For further details respecting the chemistry of fermented bread, the reader is referred to Dumas, Traité de Chimie appliquée aux Arts, t. vi. 1843; Johnston's Lectures on Agricultural Chemistry, 2d edit. 1847; and Payen, Précis de Chimie Industrielle, 1849.].

The general dietetical properties of bread resemble those of wheat-flour (see ante, p. 124). In diabetes, its use is objectionable on account of its augmenting the saccharine condition of the urine [Bouchardat (Comptes Rendus, Nov. 1841, p. 942) suggested the use of a gluten-bread, in diabetes, as a substitute for the ordinary wheaten-bread, but in practice it has not been found available. When quite devoid of starch, it can be masticated only with extreme difficulty, and in fact, is not edible.—Bran-bread is, perhaps, the best kind of bread for diabetic patients. Dr. Prout (Stomach and Renal Diseases, 5th. edit. p. 44, 1848) has published a receipt for a bread of this kind devised by his patient, the late Rev. J. Rigg. The following formula yields the best product which I have seen, and has proved highly useful in one case of diabetes: Take coarse wheat-bran, wash it thoroughly with water on a sieve, until the water passes through clear; then dry it in an oven, and grind to a fine powder by a mill (the mill which was found to answer was made by White, in Holborn). Then take 7 eggs, 1 pint of milk, ¼ lb. of butter, a few caraways or some ginger, and make it into a paste with a sufficiency of the bran-flour. Divide the mass into seven equal parts and bake each separately, in a saucer, by rather a quick oven; the time required for baking is usually about 20 minutes.—Dr. Percy (Chemical Gazette, March 15, 1849) has published a receipt for a bread for diabetic patients made of the ligneous matter of potatoes (see the article Solanum tuberosum).]. In some forms of dyspepsia, fermented bread disagrees with the patient; and, in such, benefit is occasionally obtained by the substitution of unfermented bread. The use of bown bread as a preventive of habitual costiveness has already been referred to (see ante, p. 124). It, however, frequently fails to produce the desired effect.

Fermented bread is employed both in medicine and pharmacy. Crumb of bread (mica panis) is sometimes used in the formation of pills; but is objectionable for this purpose, on account of the pills thus made becoming excessively hard by keeping. Furthermore, in some cases, the constituents of bread decompose the active ingredients of the pills. Thus, the chloride of sodium of bread decomposes nitrate of silver. Crumb of bread is most valuable for the preparation of poultices. The bread-and-water-poultice is prepared by covering some bread in a basin with hot water: after it has stood for ten minutes, pour off the excess of water, and spread the bread about one-third of an inch thick on soft linen, and apply to the affected part. Sometimes lint dipped in oil is applied beneath the poultice [Abernethy, Lancet, vol. v. 1824, p. 135.]. Decoction of poppy, or Goulard's water, may be substituted for common water. This is a valuable application to phlegmonous inflammation. A bread-and-milk-poultice, to which lard is sometimes added, is also used to promote suppuration; but it should be frequently renewed, on account of its tendency to undergo decomposition. Both poultices are used in the treatment of irritable ulcers.

β. Panis sine fermento; Panis azymus; Unfermented Bread.—Of this there are two kinds; one compact and heavy, the other light and elastic.

Of the heavy and compact kind of unfermented bread we have an example in the common sea-biscuit or ship-bread (panis nauticus), which, on account of its hardness and compactness, must be more slowly permeated and acted on by the gastric juice than the ordinary light and porous fermented bread. These biscuits are frequently adulterated with chalk. Some dyspeptics prefer the lighter kinds of biscuits (panis biscoctus) to fermented bread. Biscuit powder is frequently used for infants' food.

The light and porous kinds of unfermented bread owe their lightness and porosity to some volatile or gaseous body developed in the dough by either heat or chemical action. In the preparation of certain kinds of biscuits, solid sesquicarbonate of ammonia is used to produce lightness. The heat of the oven volatilizes the salt, the vapour of which distends the dough. Carbonic acid (developed by the action of an acid on an alkaline carbonate) is, however, the agent generally employed to give porosity to unfermented bread. The patent unfermented bread is a preparation of this kind. The following receipt yields an excellent product: Take of Flour ℔j; Bicarbonate of Soda 40 grains; Cold Water half a pint, or as much as may be sufficient; Muriatic Acid of the shops 50 drops; Powdered White Sugar a teaspoonful. Intimately mix the bicarbonate of soda and sugar with the flour, in a large basin, by means of a wooden spoon. Then gradually add the water with which the acid has been previously mixed, stirring constantly, so as to form an intimate mixture very speedily. Divide into two loaves, and immediately put them into a quick oven.—If any soda should escape the action of the acid, it causes one or more yellow spots, which, however, are more unsightly than detrimental [The above formula yields a bread of excellent quality, as I can vouch from having repeatedly employed it. Various other formulae have been published, many of which doubtless also yield excellent products. The following are given in a little pamphlet entitled Instructions for making Unfermented Bread, by a Physician, 15th edit. 1848:—

To make White or Flour Bread.

To make Brown or Meal Bread.

In the shops are sold powders under various names (such as Borwick's Original German Baking Poder for making Bread without Yeast; and Edwards's Egg Powder) to enable persons to prepare a light bread without yeast, or even light puddings without eggs. They are usually mixtures of tartaric acid and carbonate of soda, with some farinaceous substance (wheat flour and potato starch); to which is sometimes added a small portion of alum. They are very useful and convenient preparations; and, for employment on board ship, and in various other situations, will be found very valuable.]. The sugar may be omitted if thought desirable. This kind of bread is well adapted for the use of invalids and dyspeptics. With the latter it sometimes agrees when ordinary fermented bread disagrees. It is superior to biscuits in lightness and porosity. It is a very convenient kind of bread for persons on ship-board and in other places where yeast cannot be procured.

The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1854.