LABORATORY WORK ON LOCO-WEED 

 INVESTIGATIONS. 



By Albert C, Crawford, Pharmacologist, Poisonous-Plant Investigations. 



SUMMARY OF LABORATORY WORK. 



(1) Conditions analogous to those found in locoed animals occur 

 in portions of the world other than the United States, especially in 

 Australia. 



(2) The symptoms described in stock on the range can be repro- 

 duced in rabbits by feeding extracts of certain loco plants. Those 

 especially referred to here under the term " loco plants " are Astra- 

 galus mollissimus and Arag alius lamberti. 



(3) The production of chronic symptoms in rabbits is a crucial 

 test of the pharmacological activity of these plants. 



(4) It is the inorganic constituents, especially barium, which are 

 responsible for this poisonous action, at least in the plants collected 

 at Hugo, Colo. ; but perhaps in future loco plants from other portions 

 of the country may be found to have other poisonous principles. 



(5) There is a close analogy between the clinical symptoms and 

 pathological findings in barium poisoning and those resulting from 

 feeding extracts of certain of these plants. Small doses of barium 

 salts may be administered to rabbits without apparent effect, but 

 suddenly acute symptoms set in analogous to those reported on the 

 ranges. 



(6) The administration of sulphates, especially epsom salts, to 

 form insoluble barium sulphate would be the chemical antidote which 

 would logically be inferred from the laboratory work, but of neces- 

 sity these sulphates would have to be frequently administered, and 

 their value after histological changes in the organs have occurred 

 remains to be settled. But the treatment of acute" cases of barium 

 poisoning in man is not always successful, even when sulphates com- 

 bined with symptomatic treatment are employed. The conditions 

 under which sulphates fail to precipitate barium must be considered. 



(7) Loco plants grown on certain soils are inactive pharmaco- 

 logically and contain no barium. In drying certain loco plants the 



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