POISOW. 155 POITIERS. witliout physicians' certificates or prescriptions for their use. Poisoiiirg is the crime of administering poison to a human being with intention to cause death or bodily liarm. It is punished according to the result, as in other cases where one person is will- fully or maliciously injured by another. Physi- cians may administer poisons as medicines in their discretion. See C'BlilE, and consult the authorities referred to under JIeuic.l Jueis- I'BIDENCE, Crimix.^l Law, etc. POISON ALDER. See Sumac. POISON IVY. See Ivy; Sumac. POISON OAK (Rhus Toxicodendrqn) . An American shinrb, feared because of its poison- ous qualities, said to be due to a non-vola- tile oil which produces itching, reddening, and swelling of the skin of certain individuals, but not of others. Saturated alcoholic solution of lead acetate (sugar of lead) is recommended as an antidote. See IvY; Sumac. POISON OF SERPENTS. See Snaice; Eat- TLE.SNAKE : 'irEK. POISONOUS INSECTS. See Ixsect, para- graph I'oiso/iotis Insects. POISONOUS PLANTS. Plants which contain poisonous substances in sufficient amounts to render them injurious when eaten or touched by men or animals. There is, how- ever, no sharp line of distinction between poison- ous and non-poisonous plants, ilany harmless plants, even some of our most wholesome food plants, like the potato, contain traces of sub- stances, which in a concentrated extract are violent poisons. Others, though really harmless uidess eaten in immoderate quantities, are or have been popularly reputed to be poisonous. There are, however, a number of plants of which moderate doses are known with certainty to produce in- jurious or even fatal results. A botanical classification of these would scarcely be con- venient, as the}- are scattered nearly through- out the vegetable kingdom. Yet it is a notice- able fact that certain natural families are es- pecially rich in poisonous members, whose active principles are characteristic of the family. Thus nearly all members of the Solanacese and Papa- veracea" contain narcotic alkaloids ; convulsive and cardiac neurotic poisons are characteristic of the Apocynace;Te and Loganiaceoe; prussic acid is frequent in the seeds and foliage of the Drupacea': oils and acids producing cutaneous irritation are characteristic of the Anacardiacea?. EnphorbiaccoE, and Urticaceoe : the Iridace.'e. Liliacesp, Ranunculacese, Papilionacese (Legu- minos*). UmbelliferiP, and Cucurbitaceae are also notable for their poisonous members, though several of these are equally notable for their food plants. The poisonous members of the Anaeardiaceije, such as the poison siimac and poison iy, are the most important of the plants which are poison- ous to the touch, producing inflammation of the skin ; most of the others are poisonous only when eaten. Of these some contain the active principle chiefly in the fruit or seed, such as belladonna, bittersweet, stramonium, poke, hen- bane, etc.; in others, such as water hemlock and Vol. XVI.— 11 aconite, it is chieUy concentrated in the roots or tubers, though in hemlock, as in many other cases, every part of the plant is almost equally poison- ous. In such plants as ailanthus, kalmia, and wild cherry, the foliage is especially poisonous, and the latter two have often been fatal to live stock. See the separate articles on the families and individual plants named, and the article Fungi, EDiiiLE .v.nd Poisoxors. Consult: V. K. Chestnut, Thirty I'uiaonuun Plants of the United Irllates. in Farmers' Bulletin. 80, United States Department of Agriculture. POISONS. See Toxicowgy ; Antidote. POISON SUMAC. See Dogwood. POISSON, pwa'sO.N', Simeo.v De.ms (1781- 1S40|. A French mathematician, physicist, and astronomer. He early took up the stuily of the descriptive geometry of ilonge. At the age of seventeen he entered the polytechnic school at Paris, where he soon attracted the attention of his instructors, notably of Lagrange. He held various positions as examiner and professor in this institution for nearly forty years. He was also professor of mechanics in the Faculty of Sci- ences, member of the liureau of Measures, and member of the Council of l*ublic Instruction ( 1820). He was made Baron by Napoleon au<l in 1S37 became a peer. His scientific works and me- moirs number over 300. and are devoted to mathe- matics, physics, and astronomy. The work en- joying the widest circulation is his Traite de mecanique (2 vols., 1811; 2d ed. 1833; German trans. 1S35-3C). His other notable works are: Theorie mcUhematique dc la chalcur (183.); sup- plement 1837) ; Eecherches sur la probabilite des juijt mints en matiere criminelh; et en matiiie civile (1837). His important memoirs on definite integrals and their ajiplicatiuns to physics, on calculus of variations, and on probability were published in Journal dc VEcolc Poli/tcchnique (1802-30): Mvnioircs dc I'Academie (1811-43); Connaissance des Temps (1819-27) ; and in nu- merous other journals. Arago's works, volume ii., contain a complete list of Poisson's produc- tions. POISSY, pwa'se'. A small to-wn of France, in the Department of Seine-et-Oise, situated 10 miles northwest of Paris. It has a fine church which is one of the best examples of the transition style of the twelfth century. Poissy is the birthplace of Saint Louis ( 1215 ) , and here in 1561 a famous religious conference was held between Catholics and Protestants. The town has important iron foundries. Population, in 1900, 7506. POITIERS, pwa'tyfi'. The capital of the De- partment of ^'ienne. and formerly of the Province of Poitou, in Western France. It is situated on a plateau-like jx'ninsula formed by the junction of the C'lain and the Boivre rivers, and on the Orleans Railroad. 58 miles southwest of Tours (Map: France, Go). It is an old town with narrow, crooked, and ill-paved streets. Although it is a railroad junction, its commerce and in- dustries are not very important. It is chiefly interesting on account of its ancient and medise- val remains ami associations. It is preeminently a city of churches and ecclesiastical institutions. Tlie cathedral is a Gothic-Romanesque structure of the twelfth century, with an imposing inte-
