The plant you're referring to as "Horse bean" is likely not a single species but rather a common name used for several plants with toxic properties.

Here are some possibilities:

* "Horse Bean" could be a colloquial name for " Broad bean" or " Fava bean" (_Vicia faba_). While these beans are edible for humans, they can cause a severe reaction in individuals with Favism**, a genetic condition that prevents the breakdown of certain compounds in fava beans.

* " Horse bean" could also refer to " Kentucky coffee tree" (_Gymnocladus dioicus_). All parts of this tree are poisonous, particularly the seeds, which contain cytisine, a toxic alkaloid.

* " Horse bean" might also be used to refer to " Castor bean" (_Ricinus communis_). This plant's seeds contain ricin**, a highly toxic protein that can be fatal if ingested.

To identify the specific plant you're asking about, more information is needed. It's important to avoid consuming any plant without proper identification and knowledge of its potential toxicity.

If you're concerned about a potential poisoning, contact your local poison control center immediately.