Some Const.i.tuents of the Poison Ivy Plant: (Rhus Toxicodendron).

by William Anderson Syme.

ACKNOWLEDGMENTS.

The author desires to avail himself of this opportunity to tender his thanks to those under whose guidance he has worked while a student at the Johns Hopkins University, namely to Professors Remsen, Morse, Jones, and Andrews, and to Doctors Acree and Tingle for instruction in lecture room and laboratory.

He is especially indebted to Dr. S. F. Acree, at whose suggestion this research work was undertaken, for counsel and a.s.sistance in its prosecution.

He would also thank Messrs. Parke, Davis and Co., of Detroit, Mich., for the preparation of the crude material used in this investigation, and the U. S. Department of Agriculture, Washington, D. C., for electrotypes of figures 17, 18, and 19 in Bulletin No. 20, Division of Botany.

INTRODUCTION.

Plants belonging to the natural order Anacardiaciae (Cashew family or Sumach family) are found in all the temperate climates of the world and quite frequently in semi-tropical climates. Many of these plants play important parts in economic botany, yielding dye-stuffs, tanning material, wax, varnish, and drugs. Several species are poisonous. At least three poisonous species of the genus _Rhus_ are found in the United States. These three are all common and well-known plants, but confusion frequently arises concerning them on account of the different names by which they are known in different localities. For example, poison ivy (_Rhus toxicodendron_ or _Rhus radicans_) probably the best known poisonous plant in America, being found in all the States except those in the extreme West, is often confounded with and popularly called "poison oak." The true poison oak is the _Rhus diversiloba_ of the Western States.[1] The third and most poisonous species of this plant is _Rhus venenata_ or _Rhus vernix_; it is the _Rhus vernicifera_ of j.a.pan, from which j.a.panese lac is obtained. It is popularly known in the United States as "poison sumach," "poison dogwood" and "poison elder." It grows in swamps from Canada to Florida.

As the poison ivy is by far the most common of these plants in the Eastern States, a brief description of it is given here:[2] A shrub climbing by rootlets over rocks, etc., or ascending trees, or sometimes low and erect; leaflets 3, rhombic-ovate, mostly pointed, and rather downy beneath, variously notched, sinuate, or cut-lobed; high climbing plants (_R. radicans_) having usually more entire leaves. It is found in thickets, low grounds, etc. Greenish flowers appear in June.

[Ill.u.s.tration: Fig. 1.--Poison ivy (_Rhus radicans_ or _Rhus toxicodendron_). _a_, spray showing aerial rootlets and leaves; _b_, fruit--both one-fourth natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of Agriculture.)]

[Ill.u.s.tration: Fig. 2.--Poison oak (_Rhus diversiloba_) showing leaves, flowers, and fruit, one-third natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of Agriculture.)]

In the general description of the order Anacardiaciae, Gray[3] says: "Juice or exhalations often poisonous." Whether it is contact with some part of the plant, or with the exhalation from the plant, that causes the well-known skin eruption has been a topic for discussion ever since its source was known. On account of its intangible nature there has been more speculation than experimental evidence bearing on this question, although a few investigations have been made with the object of isolating the poison. It is most generally believed that the exhalations are poisonous. Dr. J. H. Hunt[4] states that the exhalations have been collected in a jar and found to be capable of inflaming and blistering the skin of an arm plunged into it.

[Ill.u.s.tration: Fig. 3--Poison sumach (_Rhus vernix_), showing leaves, fruit, and leaf-scars, one-fourth natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of Agriculture.)]

Prof. J. J. Rein,[5] in his treatise on Lacquer Work, describes the poison of the j.a.panese lac tree, _Rhus vernicifera_, as being volatile, as do also the j.a.panese chemist Yoshida[6] and the French chemist Bertrand.[7] Recent work by Prof. A. B. Stevens,[8] however, seems to show that this poison is not volatile, and is similar to, if not identical with that obtained by Pfaff[9] from _Rhus toxicodendron_ and _Rhus venenata_.

Not many cases of internal poisoning by _Rhus toxicodendron_ are on record in medical literature. Two cases of poisoning from eating the fruit of this plant have been described.[10] The subjects of these cases were two children who had eaten nearly a pint of the fruit. The symptoms are described in detail, being in general, similar to those of alkaloidal poisoning. Warm water was given to promote emesis; afterwards large quant.i.ties of carbonate of soda were given in solution under the belief that it was an antidote to the poison. Otherwise they were treated on general principles. Both children recovered.

Another case of internal poisoning is the following:[11] Three children drank an infusion of the root of poison ivy thinking it was sa.s.safras tea. The first of these cases was diagnosed as measles, but on the appearance of similar symptoms in the sisters of the first patient, the cause of the trouble was found. All recovered.

Dr. Pfaff[12] explains the few fatal cases that have followed Rhus poisoning on the a.s.sumption that enough of the poison was absorbed through the skin to cause renal complications in persons having chronic kidney trouble. He showed that the poison, when given internally, produces a marked effect on the kidneys, causing nephritis and fatty degeneration of this organ.

The irritating action of poison ivy has been attributed at different times to the "exhalation," to a volatile alkaloid, to a volatile acid, and to a non-volatile oil. Pfaff,[13] who made the most recent investigation of this poison, obtained from the plant a non-volatile oil having the same action on the skin as the plant itself. He found this oil in all parts of the plant and concluded that it was the active principle, and that one could be poisoned only by actual contact with some part of the plant. He a.s.sumed minute quant.i.ties of pollen dust to be in the air to account for the cases of "action at a distance" so frequently quoted. Pfaff says: "In my opinion, it is more than doubtful if ever a case of ivy poisoning has occurred without direct contact with the plant or with some article that has been in contact with the plant.

The long latent period of the eruption in some cases may obviously render mistakes extremely easy as to the occasion when contact with the plant really occurred." Granting, however, that the active principle is practically non-volatile when isolated from the plant, we cannot say positively that it is not volatile in the juices of the plant, or under the influence of vital forces. It is quite conceivable that the water transpired by the leaves of the plant may carry with it a quant.i.ty of the poison sufficient to produce the dermat.i.tis on a person very susceptible to its action. It is also conceivable that a volatile poison manufactured by a living plant could become non-volatile by changes in it consequent upon the death of the plant.

Up to the present time, only three important chemical investigations of the active principle of _Rhus toxicodendron_ have appeared in medical and chemical literature, these being the researches of Dr. J. Khittel, J. M. Maisch, a pharmacist, and Dr. Franz Pfaff, of the Harvard University Medical School, to whose work reference has been frequently made. The chemical work of these investigators and their conclusions are given here in some detail for the sake of completeness.

FOOTNOTES:

[1] Chesnut. Bull. No. 20, U. S. Dept. of Agr., Div. of Botany.

[2] Man. of Bot., p. 119.

[3] Man. of Bot., p. 119.

[4] Brook. Med. Jour., June, 1897.

[5] Rein, The Ind. of j.a.p., p. 338, et seq.

[6] H. Yoshida on Urushi Lacquer, Jour. Chem. Soc., 1883, p. 472.

[7] Ann. de Chem. et de Phys., Series VII, Vol. 12, p. 125, 1897.

[8] Amer. Jour. Pharm. 78, p. 53, Feb., 1906.

[9] An account of Pfaff's work will be found in another part of this paper.

[10] Amer. Jour. Med. Sci. 51 (1866), p. 560.

[11] Med. and Surg. Rep. 17, Nov., 1867.

[12] Jour. Exp. Med. 2 (1897), p. 181.

[13] Ibid.

KHITTEL'S INVESTIGATION.

The first attempt to find the poisonous const.i.tuent of this plant was made by Khittel in 1857. His work was published in _Wittstein's Vierteljahrresschrift fur praktische Pharmacie_, VII, 348-359.[14]

Khittel obtained 37-1/2 ounces of fresh leaves of poison ivy from the botanical garden in Munich, dried them, and got a residue of 9-1/2 ounces which he a.n.a.lyzed. Not detecting anything to which the poisonous qualities of the plant could be attributed, he made another series of experiments which, as he thought, showed that a volatile alkaloid is the poisonous const.i.tuent. It was obtained by the following process: "3 ounces of the powdered leaves were infused with hot distilled water, after three days strained, expressed, the liquid evaporated to 3 ounces, and with the addition of pota.s.sa, carefully distilled to one-half. The clear, colorless distillate had an alkaline reaction, and an odor resembling henbane or hemlock. It was saturated with sulphuric acid, evaporated, and treated with a mixture of equal quant.i.ties of alcohol and ether which left sulphate of ammonia behind, the solution was evaporated spontaneously, distilled with pota.s.sa, the alkaline distillate neutralized with hydrochloric acid, and a precipitate could now be obtained with chloride of platinum. Want of material prevented further experiments."

The editor of the _American Journal of Pharmacy_ inserts the following note: "It would have been more satisfactory if the author had given some physiological evidence of the poisonous nature of the alkaloid substance obtained. It is quite interesting to hear that the hitherto intangible venom of this plant has at last been detected."

FOOTNOTES:

[14] A free translation of this paper is given in Amer. Jour. Pharm. for 1858, p. 542.

WORK OF MAISCH.[15]