ANACARDIACEAE RHUS 613 



In a recent paper by Dr. Ford there seem to be some evidences for conclud- 

 ing that immunity may be obtained. That such immunity exists may be taken 

 from the clinical symptoms that different persons are sensitive to even small 

 amounts of the poison and in other cases persons who have been poisoned be- 

 come accustomed to it. Syme in his experiments upon himself found that after 

 four or five months he was no longer susceptible to the poison. 



The experiments performed by Dr. Ford are of interest. The experimental 

 material was obtained in the alcoholic fluid extract of the native plant pre- 

 pared by Parke, Davis & Co. 



It had already been shown by Pfaff that the internal administration of his non-volatile 

 oil produced definite lesions in rabbits, the animals dying of an acute nephritic at the end of 

 14 to 15 days. Occasionally the rabbits died in acute convulsions without any microscopic 

 brain lefsions. The subcutaneous administration of the fluid extract of Rhus Toxicodendron 

 produces the same effect upon rabbits as those described by Pfaff. Rarely, the rabbits die in 

 convulsions within 24 to 48 hours, but the majority of inoculated animals succumb in from 

 8 to IS days. In addition to the nephritis an extensive necrosis and slough is found at the 

 point where the poison is introduced beneath the skin. Following the inoculation we have 

 a fairly long latent period during which the weight of the animals remains stationary. After 

 seven or eight days in a typical case, the animal loses weight rapidly, the necrosis and slough 

 develop, and the animal dies of the nephritis after the lapse of about two weeks. At times 

 the skin lesions are less marked, the damage to the kidney being the important change; an 

 intraperitoneal inoculation seems able to produce these kidney changes more rapidly than 

 does the subcutaneous method. In addition to rabbits we have found that guinea-pigs are 

 susceptible to the drug, the lesions being produced with greater certainty and regularity. 

 With these animals the necrosis and slough at the point of inoculation are more extensive, 

 while the animals die of the kidney changes in about the same time. The fatal dose of the 

 poison can be estimated for both animals with tolerable accuracy. For guinea-pigs of 250 

 gram weight, 0.25 c.c. of the alcoholic extract always represents a fatal dose; and a guinea-pig 

 of 350 gram weight practically never survives a dosage of 0.5 c.c. 



The fatal dose for rabbits of 800 grams is 1 c.c. Certain rabbits of this weight die from 

 smaller doses, but not regularly and larger animals show greater resistance. Animals of 1,800 

 to 2,000 gram weight occasionally survive 2 to 3 c.c. doses, but not more than this amount. 



Experiments were made to determine whether animals which had withstood 

 some doses of the poison were susceptible to the amounts of poison capable 

 of killing untreated animals. The experiments were made with four guinea pigs, 

 varying in weight from 450 to 900 grams and on rabbits varying in weight 

 from 800 to 2800 grams. The initial doses were small; when the animals 

 regained weight larger doses were given. It was found that the serum of im- 

 munized animals contained substances neutralizing the poisonous glucoside 

 when both were injected into susceptible animals. Goats have been immunized 

 and it is probable that immunity may be obtained in other animals. 



How to Treat the Poison Ivy Patch. Various methods of treating the 

 poison ivy have been tried. The iron sulphate, 100 pounds to a barrel of water, 

 is only partially successful. Covering with tarred paper creosoted below is 

 effective according to Dr. G. E. Stone. This writer has also shown that 

 sodium arsenate (commercial) at the rate of 2 pounds to 10 gallons of water 

 poured around the roots is effective. 



Rhus glabra L. Smooth Sumach 



A low shrub from 2-12 feet high, stems with large pith, brownish bark; 

 compound leaves 11-31; leaflets pointed serrate, whitish beneath green above; 

 flowers borne in a large panicle, greenish, polygamous; calyx small 5-parted : 

 petals 5; stamens 5, inserted under the edge of a flattened disk; pistil with a 

 1-celled and 1-ovuled ovary; styles 3, terminal; fruit red, small 1-seeded. 



