Dr. Sayre’s failure to find any poisonous principle in the plants, or any toxic action on frogs, dogs or cats, cannot be received as conclusive in face of the results reached by others. Perhaps Dr. Sayre’s specimens were not grown under the proper conditions, or were not collected in the proper season to secure the toxic ingredient. Miss C. M. Watson, of Ann Arbor, Mich., succeeded in separating a small amount of alkaloid from the root of Oxytropis Lamberti, but did not apply the crucial test of physiological experiment. In the Report of the Department of Agriculture for 1879, are given analyses of Oxytropis Lamberti, Astragalus Mollissimus and Sophora Speciosa, in each of which a small amount of alkaloid was found. In 1888–9, Dr. Mary Gage Day, of Wichita, Kansas, made careful experiments on cats and rabbits, under the supervision of Dr. Vaughan in the Michigan Laboratory of Hygiene. She used a decoction of roots, stems and leaves of plants gathered in September and gave 60 to 70 c.c. of this to a half-grown vigorous kitten daily, along with abundance of milk and other food. In two days the kitten became less active, showed rough coat, increased desire for the _loco_, with partial loss of appetite for other food, diarrhœa came on, and retching and vomiting occasionally occurred. The expression became peculiar and characteristic. These symptoms increased, and emaciation advanced, and on the 18th day periods of convulsive excitement supervened. These were sometimes tetanic, the head being thrown backward and the mouth frothing. At other times the kitten stood on its hind limbs and struck the air with its fore paws, then fell backward and threw itself from side to side. There were short intervals of quiet, life being indicated by breathing only. After 36 hours of these intermittent convulsions paraplegia set in, and the kitten died in two hours. There was no apparent loss of consciousness before death. Post mortem examination revealed gastric and duodenal ulcers, some of which were nearly perforating. The heart was in diastole; brain and myel appeared normal; the entire body anæmic. To a _vigorous adult cat_ 60 c.c. to 70 c.c. of a more concentrated solution were given with other food. The results were essentially the same. By the twelfth day the cat was wasted to a skeleton and very weak. Paralysis of the hind limbs came on and the cat died on the thirteenth day. As a test experiment, two strong young cats were confined in the same place, fed from the same dish, and treated in every way the same, except that the one was fed daily a decoction of the _loco_. The one fed _loco_ acquired the _loco_ disease with the symptoms described above while the other, eating ordinary food only, remained healthy.