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. [Illustration: 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 Japanese lac tree, _Rhus vernicifera_, as being volatile, as do also the Japanese 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 quantities 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 sassafras 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 assumption 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.