506

ELEMENTS OF MATERIA MEDICA.

Degree of Dilution.

Sulphate of Soda. stops at 5,000

Iodideof Potassium. 10,000

Ferrocyanide of Potassium. 18,000

Potash. 20,000

Carbonate of Soda or of Potash. 60,000

Chromate of Potash. 100,000

Hydrosulphuric Acid. 500,000

Physiological Effects.— 1. Metallic lead. —I believe tliat so longas lead retains its metallic form it is inert. In a French journal ( Journ.de Med. de Leroux, xxiii. 318) we are told that three ounces and sixdrachms of this metal have been given to a dog without any obviouseffects. As, however, it is a metal which is readily oxidated, itoccasionally proves active when swallowed, in consequence of its beingacted on and oxidized by the contents of the alimentary canal. Aninstance of this kind is mentioned by Paulini ( Miscell. Nat. Cur. Dec. ii.Ann. vi. App. p. 7. quoted by Voigtel, Arzneimitellehre), in which colic wasproduced by swallowing a leaden bullet. Proust {Ann. de Chim. lvii. 84)says, that the alloy of lead and tin may be swallowed with impunity, inconsequence of its being much less easily oxidated than the pure metal.

2. Of the preparations of lead, (a.) On vegetables. —Marcet found thesolution of acetate of lead injurious to plants ; but Wiegmann declares itto be inert, and ascribes its inertness to the formation of an insoluble salt(carbonate) of lead by the carbonic acid of the roots of plants.

(/}.) On animals. —The preparations of lead are, for the most part,energetic poisons. The sulphuret, however, appears to be inactive, ornearly so ; for Orfda ( Toxicol. Gen.) gave an ounce of it to dogs withoutobserving any ill effects ; four ounces have even been given to horseswithout any unpleasant results. The sulphate, also, according to Orfila,is inactive. Our knowledge of the effects of the salts of lead on animalsis derived from experiments made with the acetates, nitrate, andcarbonate. The first two act as corrosives: all affect the nervous system,manifested by convulsions, palsy, and colica pictonum. (Cliristison,Treat, on Poisons, 50(1 et seq. 3d ed.)

(c.) On man.— Mr. Braid (Cliristison, op. cit. 518) states that workmenwho dig and pulverize the ore (sulphuret of lead), at the lead-mills inLaneashire, never have the lead colic until they work at the smelting-furnaces.

Most, if not all, the other preparations are more or less active; theeffects and symptoms, however, vary with the dose.

In small doses these preparations act on the alimentary canal asastringents ; checking secretion and causing constipation. These maybe regarded as the local effects. When absorbed, the constitutionaleffects of lead are observed: the arteries become reduced in size andactivity, for the pulse becomes slower and smaller; the temperature ofthe body is diminished ; and sanguineous discharges, whether natural orartificial, are frequently checked, or even completely stopped. Thisconstringing and sedative effect seems extended to the secreting andexhaling vessels; the discharges from the mucous membranes, theexhalation from the skin, and the urine, being diminished in quantity.Thus we observe dryness of the mouth and throat, thirst, greater solidityof the alvine evacuations, diminution of the bronchial secretion, and of