[17] Stevens. Amer. Jour. Pharm. 77, 255, June, 1905. [18] Whenever it is stated in this paper that a solution was poisonous or not poisonous, the test was made by the writer upon himself. [19] Liebig's Annalen, CXI, p. 215. [20] Ueber Mategerbstoff, p. 20. [21] Bull. Soc. Chim. (II), Vol. 2, 95 (1864). [22] Berichte 19, 1735 (1886). [23] Jour. Chem. Soc. 71, 1194 (1897). [24] Berichte 19, 1740. [25] Ibid. 1747; Annalen, 112, 97. [26] Biochem. Pflan. II, 521. [27] Ann. de Chim. et de Phys., 6th Series, XXII, 76 (1891). [28] Treatise on Chem., Vol. III, Pt. III, 492. [29] Les Sucres; Chem. der Zuck.; Biochem. der Pflan. [30] Chem. Zeit. 23, Rep. 177. [31] Loc. cit. 1, 209. [32] On standing several weeks, a small quantity of tar separated out on the walls of the vessel, also a brown precipitate which was filtered off, suspended in water, and hydrogen sulphide was being passed in when an accident occurred and it was lost. [33] "By warming with alkalies or barium hydroxide, rhamnose is colored yellow." Chem. der Zuck. I, 177. [34] Ibid. 188. [35] Ibid. [36] Rayman, Sur L'Isodulcite, _Bull. Soc. Chim._ 47, 668 (1887). [37] Acides Gummiques. [38] Berichte XX, pp. 1089, 1091, 1188, 2566. [39] Ann. de Chim. et de Phys. (6) XXII, 93 (1891). [40] Biochem. der Pflan. I, 210. [41] Comptes rendus CXV, 892. [42] Amer. Chem. Jour. 28, 370. [43] Amer. Jour. Pharm. 77, 255 (June, 1905); 78, 53 (Feb., 1906). [44] A wax obtained from _Rhus succedanea_ was shown by Stahmer to contain palmitic acid and glycerol in the form of glycerol palmitate. _Annalen_ 43, 343, (1842). [45] See Amer. Jour. Pharm. 77, 256. [46] This section is added in the hope that it may be of use to others who are subject to this form of poisoning. [47] Moor, N. Y. Med. Rec. 45 (1894), 200. [48] Bull. No. 26, U. S. Dept. Agr., Div. of Bot. 47. [49] Lacerda, Comptes rendus 93 (1881) 466-469. [50] Amer. Jour. Med. Sci. 52 (1866), 285. SUMMARY. Leaves and flowers of the poison ivy plant were extracted with ether and the ether was removed by evaporation. In the residue, the following substances were found and studied: gallic acid, fisetin, the sugar rhamnose, and a poisonous tar, gum, or wax. The lead compound of the poison was soluble in ether; this fact gave a means of separating the poisonous substance from the non-poisonous matter in one operation. The poison was not volatile with vapor of acetic acid, or with vapor of alcohol. The poisonous tar or wax was decomposed by acids and yielded gallic acid, fisetin, and rhamnose, showing the probable source of these compounds in the plant, and indicating that the poison is a complex substance of a glucoside nature. It was found that a portion of the poisonous substance could be precipitated by lead acetate from a solution of the purified tar in 50 per cent. alcohol. All cases of poisoning developed on the writer were easily cured with potassium permanganate.