ARSENIOUS ACID.

385

water which contained of its weight of arsenic. And, more recently,Gilgenkrantz ( Journ. de Pharm. xxiii. 38) says he has seen an algaceousplant, of the genus either Leptomitus or Hygrocrocis, dev elope itself in asolution of arsenic. These are most remarkable exceptions to the generaleffects of this poison on vegetables, and deserve further examination.Jager has shewn that arsenic is absorbed by plants : for he found that onburning vegetables destroyed by this poison he obtained a garlic odour.

(, b.) On animals generally. —Arsenious acid is poisonous to all classesof animals. No exceptions, I believe, are known to exist to this state-ment. The most extensive series of experiments on this subject arethose performed by Jager {op. cit .) From them we learn that in allanimals, from the infusoria up to man, death from arsenic is invariablypreceded by inordinate actions and increased evacuations, especially fromthe mucous membranes. In most animals the stools were frequent andfluid; and in those in which mucus is secreted on the surface, it wasremarkably increased. The power of voluntary motion and susceptibilityof external stimuli were decreased; and after death the muscles soonceased to be influenced by the galvanic agency. In animals whichbreathe by lungs, respiration became difficult and laborious; and inwarm-blooded animals great thirst was experienced. In birds and mam-mals convulsions came on, preceded by vomiting, except in those animals(as the rabbit) which cannot vomit. Enormous quantities of arseniousacid have been sometimes administered to horses with impunity. Berthe(Recueil de Med. Vet. Oct. 1825) gave 2 and afterwards 3 drachms to amare, for the cure of an obstinate skin disease, without any injuriouseffects. Beissenliirz (quoted by Wibmer, die Wirkung, &c. i. 317) gavesuccessively, on different days, 1, 4, 3, 2, and 8 drachms of arsenious acidto a horse: the animal did not die until the ninth day after taking thelast-mentioned dose. Yet notwithstanding these and some other analo-gous facts, which seem to prove that arsenic has comparatively little effecton horses, the best informed veterinarians agree in considering it anenergetic poison to these animals. (See the evidence of Mr. Bowles, inthe Ed. Med. and Surg. Journ. viii. 351.)

( c.) On man. a. Of very small or therapeutical doses. —In very smallquantities (as fg or -J-j of a grain) no obvious effects are usually producedby the use of arsenic, unless it be continued for a long period. Indeedsome writers (e. g. Vogt, Pharmakodyn.) go so far as to assert that it is astrengthening remedy, and that it improves the appetite, invigoratesdigestion, promotes assimilation and secretion, excites the muscular andnervous functions,—in a word, acts as a tonic. I cannot, however, sub-scribe to this doctrine, because I have never been able to see the effectshere asserted. It is, indeed, true that patients sometimes experience atemporary increase of appetite from the use of small doses of arsenic ; andit is also certain that this remedy is frequently beneficial in agues andother diseases in which tonics have been found efficacious. But theanalogy between the action of arsenious acid and that of the vegetabletonics (as cinchona, to which Vogt compares it) stops here. I havesought in vain for other evidences of a tonic operation. I have seenvery minute doses of arsenic given to patients affected with lepra, andcontinued for many days, without being able to detect the least indicationof its action on the system, except the amelioration of the disease. When