_Toxic Principle._ Authorities differ as to the substances to which the toxic property, if any, is to be attributed. According to Ludwig the milky juice, known as _Lactucarium_, includes _Lactucone_, _Lactucin_, and _Lactucic Acid_, the second of these being the narcotic substance. Nearly half the weight of _Lactucarium_ (a form of dried juice) consists of the tasteless inodorous _Lactucone_ or _Lactucerin_ (C_{14}H_{22}O), and the bitter taste is due to _Lactupicrine_, Lactucin and Lactucic Acid. In the leaves of _L. virosa_, Dymond found traces of _Hyoscyamine_ or a similar substance (_Jour. Chem. Soc._, 1892, Vol. 61, p. 90). _Symptoms._ Intoxication is produced similar to that caused by poppy heads; the narcotic effects are dominant (Cornevin). REFERENCES. 11, 73, 81, 130, 213, 240. 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:—