The toxicity of one or more of the Astragali was observed by the Spaniards during their exploration of the Southwest in the sixteenth century. They observed peculiar nervous disturbances in their horses which they attributed to the grazing of certain plants and their designation of "loco" for members of this genus is still employed to designate all the plants in the Astragalus and Oxytropis genera which possess this peculiarity. With the toxicity of a large group of related plants well established it appears remarkable that so many years would pass before the toxicity of a second group of Astragali, the vetches, would be recognized and a new disease entity established.
Mathews, Frank P.
"The Poisonous Astragali,"
Iowa State University Veterinarian: Vol. 9
, Article 7.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol9/iss1/7