Prep. During the fermentation of an infusion of malt, by the action of yeast, a fresh formation of the ferment (yeast) is produced from the albuminous principles contained in the malt.

Prop. & Comp. Yeast is a yellowish or greyish white, viscid, frothy liquid, having a characteristic odour and a peculiar bitter taste; under the microscope it is found to consist, for the most part, of separate oval confervoid cells or vesicles. The plant is called the Torula cerevisiae. In composition yeast resembles gluten or albumen, but it is in an active condition, and possesses the property of exciting the vinous fermentation in saccharine solutions.

Off. Prep. Cataplasma Fermenti. Yeast Poultice. (Beer yeast, six fluid ounces; flour, fourteen ounces; water heated to 100°, six fluid ounces. Mix the yeast with the water; add the flour, and stir until a cataplasm is made. Place it near the fire until it rises.)

Therapeutics. Yeast, when externally applied, acts as a stimulant and antiseptic, and in the form of cataplasm or poultice is employed to correct the discharges of indolent ulcers. Internally it has been used in low states of the system, to prevent the formation of boils and carbuncles, and as a remedy in diabetes: in the latter disease there has been no proof given of its efficacy.

Dose. From a dessert to a tablespoonful. Fresh yeast should be employed.