POISONING FROM OTHER PLANTS 39 



In the advanced stages the animals become frantic, hence the name "loco" 

 or crazy. Horses and sheep are the most susceptible, although cattle are also 

 a-ffected. 



Of the various species of loco weed, the stemless loco Oxytropis Lamberti 

 Pursh}, and the woolly loco weed (Astragalus nwllisismus Torr), are the most 

 injurious. These weeds grow luxuriantly on sandy ranges and appear early in 

 the spring when other vegetation is scarce, and since they retain their fresh 



Fig. 9. Loco Weed (Astragalus nwllissiniiis) , U. S. Dept. Agrl. 



green color during the entire summer they prove especially attractive to stock. 



Recently the poisoning has been attributed by Dr. Crawford and others of 

 the U. S. Dept. of Agrl., to mineral salts in the plant. 



The period of greatest danger is chiefly during the month of May. 



Symptoms. The symptoms, which are referable to the nervous system, are 

 attributable to the narcotic effect of the plant. They appear slowly and are ap- 

 parently divisible into two stages. The first stage is characterized by the follow- 

 ing symptoms : Stupor, defective vision, unnatural movements and apparent hal- 

 lucinations. When excited the animals become frenzied. The coat becomes 

 shaggy, the teeth grow long and become loose, and a depraved appetite which 

 is very marked, is developed. The animals prefer the loco weed to wholesome 

 food, and will dig up the roots and eat them to satisfy their craving. 



In the second stage there is emaciation, exhaustion, feeble movements 

 and finally death from starvation. The course of the disease is quite variable 



