This is prepared, by means of the vinous fermentation, from an infusion of malt, which is made from barley, by exposing it to a moderately elevated temperature with moisture, so as to promote germination, and then drying the germinated grain by artificial heat. In the germination of barley, there is first generated a nitrogenous principle called diastase, through the agency of which the starch of the grain is converted into grape sugar This is extracted by infusion, and along with it a matter which is capable of acting as a ferment. Hops are added to the infusion, and the liquid is exposed to a temperature favourable to vinous fermentation. The result is malt liquor, which differs according to the quantity and character of the malt employed. Three prominent varieties are recognized; namely, table beer, ale, and porter. In the drying of the malt, it is exposed to different temperatures from 100° Fahr. upward. When dried at the lowest temperature, it undergoes little change of colour, and is called pale malt; at a greater heat, but insufficient to decompose it, the colour is changed to amber brown; and, at a high heat, it is roasted and charred, losing its characteristic properties to a considerable extent. In the preparation of ale, the pale malt is used; in that of beer, the brownish; and in that of porter, the same with the addition of some of the roasted malt to deepen its colour. Table beer, in which but a small proportion of malt is used, contains insufficient alcohol to preserve it, and is therefore apt to spoil in hot weather. It is unfit for medical use. and may be left out of consideration.

Composition

Malt liquor, besides alcohol and water, contains sugar. gummy and extractive matters, and gluten, derived from the malt; a bitter principle and volatile oil, from the hops; and lactic and carbonic acids, the product of the chemical change in fermentation. There are also various salts of little or no importance. The bitterness of the liquor is owing to the bitter principle of the hops, and its aroma in part to their volatile principle.

Ale owes its light colour to the paleness of the malt. According to the analysis of Brando, it contains on an average 6.87 per cent. by measure of alcohol of the sp. gr. 0 825, and of course has somewhat more than one-half the average strength of the light wines.

Porter is very dark-coloured in consequence of the burnt malt used along with dried malt in its preparation. For the same reason it is somewhat weaker when prepared from an equal amount of malt; for the portion burnt has lost its virtues. The alcoholic strength of London porter, as given in Brando's table, is 4.20 per cent, of brown stout 6.80 per cent.

The carbonic acid in malt liquors is owing to the incompleteness of the fermentation when they are bottled. In consequence of having a smaller proportion of alcohol than the wines, they more readily become sour on exposure, and are often unfit for use.

Effects on the System

So far as their alcohol is concerned, these liquors do not differ from the wines in their effects; and the remarks made upon the modified influence of the alcohol as existing in the latter, are equally applicable to the former. But the malt liquors are richer in nutritive matters, leaving the alcohol out of consideration, than the wines, and have, in addition, the properties of the hops employed, which are actively tonic, and exercise a decided narcotic influence on the brain, producing a tendency to drowsiness. Hence ale and porter, while they are capable of stimulating to intoxication, are less enlivening and exhilarating than the wines, and more tonic and soporific. When perfectly sound,they usually agree well with the stomach; but in the dyspeptic, though the hops they contain act favourably on the digestion, they are not unfrequently injurious by their acescent tendency.

Therapeutic Application

The malt liquors may be used for the same general purposes as the wines; but they cannot compete with (hem in any case in which the stomach is in a delicate state; and are therefore generally unsuited to acute diseases. In the convalescence, however, from these affections, when the stomach is no longer diseased, they are often preferable to the wines, as less stimulating and more tonic.

For the same reason, they are better suited to chronic cases, in which the indication is for the habitual employment of supporting measures, as in scrofulous or tuberculous affections. Persons disposed to these complaints, or labouring under them, may often advantageously make use of ale or porter, to the amount of a pint or more in twenty-four hours.

They are also an excellent substitute for the stronger alcoholic drinks, when it is desired gradually to correct habits of intoxication; the hops they contain acting usefully towards obviating the wakefulness and nervous disorder, so apt to ensue upon a material diminution of the stimulus. But it must be understood that the porter or ale also must be ultimately withdrawn.

In the treatment of delirium tremens, it is often sufficient to allow the patient the free use of malt liquors in connection with the opium used; or, if ardent spirit is employed, it should as soon as possible give way to these milder stimulants.