Another method for the manufacture of an extemporaneous lens, by Mr Francis, is the following:—Procure a piece of thin platinum wire, and twine it once or twice round a pin’s point, so as to form a minute ring with a handle to it. Break up a piece of flint glass into fragments a little larger than a mustard seed; place one of these pieces on the ring of wire, and hold it in the point of the flame of a candle or of a gas-light. The glass will melt and assume a complete lens-light or globular form. Let it cool gradually and keep it for mounting. It may be mounted by placing it between two pieces of brass which have corresponding circular holes cut in them of such a size as to hold the edge of the lens.
LEN′TIL. Syn. Lens, L. The seed of the Ervum Lens, a plant of the natural order Leguminosæ. The lentil is considerably smaller than an ordinary pea, and is of the shape of a double convex lens. Several varieties are cultivated on the Continent of Europe and in many parts of Asia, where they are largely consumed as human food. Lentils are more nourishing than any other description of pulse, but are reputed difficult of digestion, apt to disorder the bowels, and injurious to the eyes. Several alimentary preparations, sold at high prices as cures for dyspepsia, constipation, &c., contain lentil flour as the principal ingredient.
Composition of Lentils.
| Nitrogenous matter | 25·2 |
| Starch, &c. | 56·0 |
| Cellulose | 2·4 |
| Fatty matter | 2·6 |
| Mineral matter | 2·3 |
| Water | 11·5 |
| ——— | |
| 100·00 |
(Payen.)
Lentils on account of their difficult digestibility require to be very thoroughly cooked. See Ervalenta and Revalenta.
LEPROSY. Syn. Lepra. A disease of the skin distinguished by circular scaly patches.
LEPTANDRIN. A peculiar crystalline principle obtained from the root of Leptandra Virginica, a North American plant belonging to the nat. order Scrophulariaceæ. Leptandrin is chiefly employed in American medical practice as a cathartic and cholagogue, in which latter function it has been recommended as a substitute for mercury. It is stated to be very serviceable in cases of duodenal indigestion
and chronic constipation.—Dose, 1⁄4 to 1⁄2 grain.
Mr Wayne obtained leptandrin by adding subacetate of lead to an infusion of the root, filtering, precipitating the excess of lead by carbonate of sodium, removing the carbonate of lead by filtration, passing the filtered liquid through animal charcoal to absorb all the active matter, washing the charcoal with water till the washings began to be bitter, then treating it with boiling alcohol, and allowing the alcoholic solution to evaporate spontaneously. By dissolving the powder thus obtained in water, treating this with ether, and allowing the ether to evaporate, needle-shaped crystals were obtained, which had the bitter taste of the root. Leptandrin is soluble in water, alcohol, and ether.