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ELEMENTS OF MATERIA MEDICA.

or purgative effects from it; but he experienced headache and disturbeddigestion. Dr. Cullen {Mat. Med.) says, “ I have known four ounces ofit taken at once, and soon after four ounces more, without any sen-sible effect.” The local operation of this solution is that of a mildstimulant.

Uses — (a.) Internal. —It is employed in febrile and inflammatory dis-eases, and forms a constituent of the ordinary saline draught. It isgiven in conjunction with nitrate of potash, or tartar emetic, and some-times with camphor and opium. When administered as a diaphoretic,its operation is to be promoted by the use of tepid diluents and externalwarmth. Its diuretic effect is assisted by keeping the skin cool, andconjoining the spirit of nitric ether.

[b.) External. —Diluted with water it is sometimes applied as a dis-culient wash to inflamed and bruised parts. Mixed with six or seventimes its volume of rose-water, to which a drachm or two of tincture ofopium may sometimes be added, it is employed as a collyrium in chronicophthalmia.

Administration. —It is given in doses of half a fluid ounce to two orthree ounces every five or six hours.

Order 7.—Carbon, and its Compounds with Oxygen, Hydrogen,

and Nitrogen.

Carbo'nium. — Car'bon.

History. —The term carbon (from carbo, onis, coal) was first employedby Morveau, Lavoisier , and Bertliollet, to designate the pure matter ofcharcoal. To the second of these chemists, w'e are indebted for demon-strating, that by combustion in oxygen gas the diamond and charcoal yieldthe same product; namely, carbonic acid gas.

Natural History. —Carbon is found in both kingdoms of nature:

(a.) In the inoryanized kingdom. —When pure and crystallized it con-stitutes the diamond, which Sir D. Brewster ( Edinb. Phil. Journ.vol. iii. p. 98, and Philosoph . Mag. vol. i. p. 147, 1827) suspects tobe of vegetable origin; but a specimen described by Mr. Ileuland{Geol. Trans., 2nd series, i. 419), was found in a primary rock. Plum-bago and anthracite consist principally of carbon. The bituminoussubstances (as coal, petroleum, naphtha, &c.) also contain it. These areadmitted by geologists to be of vegetable origin. Carburetted hydrogenis evolved from coal strata, marshy places, stagnant waters, &c. Car-bonic acid is found either in the free state, as in the atmosphere, inmineral waters evolved from the earth in old volcanic countries, &c., orcombined with metallic oxides, in the form of the carbonate of lime,iron, &c. It is remarkable that carbon is rare among the older rocks(De la Beche , Researches in Theoretical Geology, p. 32).

{b.) In the organized kingdom. —Carbon is an essential constituent ofall organized beings, vegetable or animal.

Properties. —Carbon is a solid, odourless, tasteless substance, neitherfusible (?) nor volatile; combustible in oxygen gas, yielding carbonicacid gas. Its equivalent by weight is 6. Some years since Dobereiner asserted that he had discovered a metallic basis in it, but his statementhas not been confirmed.

The other properties of carbon are so varied, that chemists are obliged