An extensive class of poisonous compounds, probably protein, of which some occur in plants, some constitute the poisonous products of bacteria, and some are the poisonous agents in the venom of snakes, scorpions, the tarantula, the Gila monster, spiders, and other poisonous animals.

It is characteristic of these substances that their poisonous symptoms come on only after a latent period, and that, in susceptible animals, immunity to the poison may be established by the repeated administration of small doses. This immunity is specific, the immunity to one toxin conferring no protection from poisoning by another.

Aside from those produced by bacteria and animals, the most important known toxalbumins are:

1. Ricin, which occurs in the castor-oil bean, the seed of Ricinus communis. The poisonous ricin is left behind in the extraction of the castor oil; but there have been some cases of poisoning from the ingestion of the whole seeds. The author has met with a case in New York. The symptoms are violent gastro-enteritis and collapse.

2. Abrin, which occurs in jequirity beans (Abrus precatorius), the little shiny red seeds with circular black spot which one often sees in the shops in baskets of sea-shells. It is used as an irritant in the eye in some cases of corneal opacity.

3. Amanita toxin, which occurs in the death's head fungus, Amanita phalloides, and is responsible for many cases of mushroom-poisoning. (See under Muscarine.)

Hypersusceptibility to a toxalbumin in the pollen of certain plants would seem to be the explanation of the attacks of hay-fever and hay-asthma to which so many people are subject (Meltzer and Auer and Wolff-Eisner).