C. Lichens as Poisons
Though the acid substances of lichens are most of them extremely irritating when taken internally, very few lichens are poisonous. Keegan[1284] writing on this subject considers this quality of comparative innocuousness as a distinctive difference between fungi and lichens and he decides that it proves the latter to be higher organisms from a physiological point of view: “the colouring matters being true products of deassimilation, whereas those of fungi are decomposition or degradation waste products of the albuminoids akin to alkaloids.”
The two outstanding exceptions to this general statement are the two Alpine species Letharia vulpina and Cetraria pinastri. The former contains vulpinic acid in the cortical cells, the crystals of which are lemon-yellow in the mass. Cetraria pinastri produces pinastrinic acid in the hyphae of the medulla and the crystals are a beautiful orange or golden yellow.
These lichens, more especially Letharia vulpina, have been used by Northern peoples to poison wolves. Dead carcasses are stuffed with a mixture of lichen and powdered glass and exposed in the haunts of wolves in time of frost. Henneguy[1285], who insists on the non-poisonous character of all lichens, asserts that the broken glass is the fatal ingredient in the mixture, but Kobert[1286], who has proved the poisonous nature of vulpinic acid, says that the wounds caused by the glass render the internal organs extremely sensitive to the action of the lichen.
Kobert, Neubert[1287] and others have recorded the results of experiments on living animals with these poisons. They find that Letharia vulpina either powdered or in solution has an exciting effect on the mucous membrane. Elementary organisms treated with a solution of the lichen succumbed more quickly than in a solution of the acid as a salt. Kobert concluded that vulpinic acid is a poison of protoplasm.
He further tested the effect of the poison on both cold- and warm-blooded animals. Administered as a sodium salt, 4 mg. proved fatal to frogs. The effect on warm-blooded animals was similar. A sodium salt, whether swallowed or administered as subcutaneous or intravenous injections, was poisonous. Cats were the most sensitive—hedgehogs the least—of all the animals that were subjected to the experiments. Volkard’s[1288] synthetic preparation of vulpinic acid gave the same results as the solution directly extracted from the lichens.