HUMULIN. The name given to a beautiful extract or essence of hops, made as follows:—
A concentrated tincture of hops is prepared by percolation with rectified spirit; the same hops are then exhausted with water; the spirit is removed from the tincture by careful distillation, and the upper aqueous portion is skimmed off, and added to the infusion, which latter is then evaporated to the consistence of a soft extract; the oleo-resinous residuum of the tincture is next added, and well mixed in;
after which the whole is put into pots and carefully tied over for sale. The product possesses all the fragrant, tonic, and bitter qualities of the hop in a highly condensed form. See Hops, Lupulin, &c.
HU′MUS. Syn. Ulmin. When wood, or woody fibre, is exposed to the joint action of air and moisture, it suffers eremacausis or decay, and crumbles down into a dark-brown or black powder commonly called ‘mould,’ and to which chemists have given the name of ‘humus.’ In this state it exists in fertile soils, in which it is derived from the decay of plants. A powder of similar composition is produced by the action of powerful chemical reagents on sugar, lignin, &c. When acted upon by dilute boiling solution of caustic potassa, this substance yields a deep-brown solution, from which acids precipitate a flocculent brown substance generally called ‘ulmic’ or ‘humic acid.’ Both bodies require further investigation, as they are supposed to vary exceedingly in composition.
HUNGER. The peculiar sensation arising from the want of food. When severe, it increases to actual pain, the coats of the stomach are acted on by its own juices, the respiration becomes less frequent, the circulation languid, and there is a general diminution of the heat of the body and of the secretions. The return of hunger is accelerated by exercise and labour, and by the exposure of the body to a low temperature. Long fasting is injurious, more particularly to the young and the debilitated. See Appetite, Nutrition, &c.
HUS′BANDRY. The business of the farmer; by some the term is restricted to the joint operations of farming and gardening on the small scale. It is also sometimes used synonymously with agriculture.
HY′ACINTH. In botany, the English name for the genus Hyacinthus. There are numerous varieties of the garden hyacinth, all very beautiful. The bulbs are largely imported from Holland, and are often grown in water contained in suitable glass vessels (hyacinth glasses). In mineralogy, the term is applied to crystallised yellow or brown zircon. See Gems.
HYDRAC′IDS. Syn. Hydrogen acids. A name formerly given to those acids which do not contain oxygen, as hydrochloric, &c. It is still occasionally employed.
HY′DRAGOGUES. Syn. Hydragoga, L. Medicines which cause the removal of water from any of the cavities of the body. Many cathartics, as gamboge, jalap, &c., are classed under this head.
HYDRAS′TIN. The name given to a concentrated remedy much employed by the medical eclectics of America.