ERICACEÆ.
Rhododendron (Rhododendron sp.). The literature points to there being no doubt as to the poisonous character of a number of species of Rhododendron, and indeed most species are suspected. Animals do not appear to eat Rhododendrons very extensively, but both English and Belgian veterinary surgeons have published records of poisoning of sheep and goats by R. ponticum. Suspected cases were recorded in the Journal of the Board of Agriculture (1907 and 1914); three cases of cattle poisoning in the Veterinary Record (1900, 1906, and 1907); one of calves in the Veterinarian (1859); and three of sheep-poisoning—one in the Veterinary Journal (1906), and two in the Veterinarian (1865); but these cases were not all fatal. The death of 19 out of 21 cross-bred Scotch lambs due to eating R. ponticum was reported by C. T. Baines in the Journal of the Land Agents Society (Aug. 1914, p. 373). The plant was eaten after a heavy fall of snow. Chesnut includes R. maximum as one of the thirty most poisonous plants of the United States. According to Cornevin, R. ferrugineum causes frequent poisoning of animals which graze on the plateaux where it grows—especially sheep and goats, the latter providing the most victims, as they willingly browse the young shoots and leaves. R. californicum is said to be poisonous to sheep in Oregon. R. Chrysanthum, the leaves of which have been used in Russia and Germany for rheumatism, has caused poisoning in man. R. punctatum and R. hirsutum appear to be not less poisonous.
Both leaves and flowers are narcotic, and even the honey in the flowers is regarded with suspicion. The following quotations are not without interest:—
“In these regions (Tungu) many of my goats and kids had died foaming at the mouth and grinding their teeth, and I have discovered the cause to arise from their eating the leaves of Rhododendron cinnabarinum (“Kema Kechoong,” Lepcha; Kema signifying Rhododendron); this species alone is said to be poisonous, and when used as a fuel it causes the face to swell and the eyes to inflame, of which I observed several instances.” (Hooker, Himalayan Journals, ii. p. 150).
“Rhododendron arboreum becomes plentiful at 5000 to 6000 feet (East Nepal), forming a large tree on dry clayey slopes.... In the contracted parts of the valley the mountains often dip to the riverbed in precipices of gneiss under the ledges of which wild bees build pendulous nests looking like huge bats suspended by their wings; they are two or three feet long and as broad at the top whence they taper downwards; the honey is much sought for except in spring, when it is said to be poisoned by Rhododendron flowers just as that eaten by the soldiers in the retreat of the Ten Thousand was by the flowers of R. ponticum.” (l.c. i. p. 200).
Toxic Principle. The leaves and flowers contain a bitter poisonous glucoside, Andromedotoxin (C31H50O10), which has been regarded as more poisonous than Aconitine. Other glucosides found in Rhododendrons are Ericolin (C34H56O21), Arbutin (C12H16O7), and Rhododendrin (C16H22O7), but it is not clearly shown whether these are poisonous when ingested; Kobert, however, includes the two former among cerebro-spinal poisons.
Symptoms. In the case of goats Cornevin records intense pain, diarrhœa, discomfort, gritting of teeth, salivation, and frequently vomiting; while there is reduced lactation, trembling, spasms, vertigo, loss of power, and death. Lander notes similar symptoms in cattle and sheep.
According to Eve (Veterinary Record, 1907), a reddish colour was observed in the milk of a cow poisoned by Rhododendron.
REFERENCES.
[4], [16], [53], [63], [73], [76], [81], [144], [161], [170], [203], [205], [211], [212], [213], [231], [252], [264].
Azalea (Azalea sp.). A suspected case of poisoning was recorded in the Journal of the Board of Agriculture in 1907. No British record of poisoning has been found. Various species of Azalea (A. pontica, A. indica, A. arborescens, A. nudiflora, etc.) are stated to be very poisonous to all animals which browse on them in the East. Cuttings should never be thrown down where they can be eaten by stock.
Toxic Principle. Little work has been done on these plants, but they are believed to contain Ericolin, Arbutin, and Andromedotoxin as in the case of rhododendrons (p. [47]).
Symptoms. Azaleas appear to be narcotic, and to produce symptoms resembling those caused by Lolium temulentum (Cornevin).
REFERENCES.