Although the poisonous properties of the mancinella have been very much exaggerated, it is nevertheless a very poisonous tree, which, happily, becomes more and more rare, owing to its being rooted up with great care wherever it shows itself. It is a tree from 12 to 15 feet high, with a trunk having a white and soft wood and covered with a greyish bark. Its branchy top gives it the appearance of a European fruit-tree. Its leaves are alternate, oval-acute, somewhat cordate at their base, with fine indentations, and a red gland at their apex. They are attached to long petioles; stipulate while young. Flowers monoïchous, forming long terminal spikes, the male flowers being above, the female below or at the axilla of the leaves. The male flowers have a bifid perianth whence emanate the stamens, the united filaments of which form a column that supports the anthers. The female flowers have a perianth with two or three divisions and a rudimentary foliole; the ovary is round and superior; style straight, terminating in 6 or 7 red, radiating, reflexed stigmata. The fruit is round, pulpy, from 5 to 6 inches in diameter, umbilicate at the top, and inclosing a wooden kernel with seven monosperm compartments. The fresh leaves are triturated. When we were informed that a mancinella had been discovered near Rio, we requested Mr. Ackermann, a pupil of the institute, to repair to the spot for the purpose of verifying the identity of the plant, and collecting its juice. Having accomplished his mission, he drunk a portion of the liquid, on the 10th of January, 1847, in a public sitting of the institute. He was joined in the proving by several of our pupils. Some of the following symptoms were so violent, that they had to be counteracted by antidotes. The pathogenesis of the mancinella is one of the most precious additions which our Brazilian provers have furnished to our Materia Medica. Prover: M. E. T. Ackermann. FIRST PROVING. _First day._—1. Merry mood, desire to sing. Is disposed to take every thing in good part. Buzzing in the ears and whizzing like the wind, when walking. Urine scanty and whitish. 5. Sensation of heat and trembling in the chest. Constant eructations like volumes of air. Watery vomiting. Violent pain in the abdomen, as if he had been struck by the point of a stick.