In 1884 there was a fatal outbreak of a disorder in horses in portions of the Missouri Valley in Iowa, Nebraska, and Dakota. This was almost uniformly fatal in a few weeks or months. The animals lost strength and became emaciated, although they were kept in pasture where there was abundant grass. There was marked stupor, the animals falling asleep while eating, and they "would remain standing for a whole week, sleeping much of the time, with the head resting upon some object." The post-mortem examination showed that "in every instance there was marked hemorrhagic effusion into the fourth ventricle, the liver and spleen were abnormally dense, the walls of the intestines were almost destitute of blood, and the stomach enormously distended with undigested food." The post-mortem find and clinical symptoms suggested to Stalker[108] that this disorder was due to some plant analogous to _Astragalus mollissimus_. He found abundant in these regions _Crotalaria sagittalis_, or rattle-box, one of the so-called loco weeds, and by the administration per os to a young horse of an infusion of 15 pounds of the plant, given in two days, produced the clinical symptoms and the post-mortem condition of the brain which he previously observed on the range. Power and Cambier[109] undertook the chemical study and the isolation of the active principle of this plant, together with that of _Astragalus mollissimus_. They found that the _Astragalus mollissimus_ if distilled with water yielded a distillate which possessed a peculiar odor, which they thought due to a trace of volatile oil. On distilling with alkali they obtained ammonia and a trace of trimethylamine. In the case of Crotalaria only ammonia was found.[110] They argued that because trimethylamine was not obtained in this case choline was not present. On distilling the _Astragalus mollissimus_ with acidulated water (H_{2}SO_{4}) the distillate was found to contain acetic acid--settling the nature of the "peculiar organic acid" described by Kennedy. From this plant they obtained a resin or mixture of resinous bodies by extracting the plant with alcohol, and after concentration precipitating with acid water. These resins in doses of from 2 to 5 grains failed to produce any symptoms in kittens.