No specific antidote for the disease caused by timber poisonvetch 

 has yet been discovered or developed; hence the problem, is one of 

 prevention. Livestock should be debarred from areas which are 

 heavily infested with this plant, especially where previous fatalities 

 have occurred. Animal newcomers to a range where this plant 

 abounds should be carefully watched to prevent their consumption 

 of excessive quantities of timber poisonvetch; areas on which it 

 occurs should be grazed lightly. 



The exact chemical nature of the toxin in this plant is unknown. 

 Beath and co-workers 3 indicate that "stock poisoned by this plant 

 exhibit symptoms suggestive of metallic poisoning. Ash analysis of 

 the plant reveals the presence of comparatively large amounts of 

 tin." The "trace" of selenium which those investigators obtained 

 in their analysis is perhaps even more significant. It is possible that 

 timber poisonvetch, like the closely related two-groove poisonvetch 

 (A. bisulcatus] and several other plant species reported by Beath 

 and co-workers, 5 may also be selenium-bearing when grown. on cer- 

 tain soils. Several indications, at least, point that way: (1) As a 

 result of the high protein content of timber poisonvetch, there is 

 the possibility of its absorbing sulphur in large quantities; hence, 

 if Hurd-Karrer's assumption of substitution of selenium for sulphur 

 in certain synthesized plant compounds 6 7 is correct, then timber 

 poisonvetch might reasonably be supposed to absorb considerable 

 quantities of selenium if that element is present and available to the 

 plant in the soil in which it grows; (2) the fact that Byers 8 reports 

 that analyses of Bridger and Wasatch shales from Uinta County, 

 Wyo., reveal no toxic amount of selenium, may explain why Beath 

 and co-workers 2 failed to obtain symptoms of poisoning after feed- 

 ing large quantities of timber poisonvetch to sheep on a range in 

 that county; (3) the symptoms caused by timber poisonvetch and 

 the autopsy results are similar to those of animals poisoned by small 

 doses of the sodium salt of selenious acid ; 5 (4) the increased losses 

 of livestock from timber poisonvetch during seasons of insufficient 

 rainfall agrees with the known fact that many of the selenium com- 

 pounds are water-soluble and, therefore, would not leach out of the 

 surface soil, as might reasonably be expected, during periods of 

 normal or sufficient rainfall. 



To sum up : Timber poisonvetch is a peculiar and important range 

 plant, of value for forage under certain conditions and, under cer- 

 tain other (as yet undetermined) conditions, virulently poisonous. 

 Further study of its occurrence, plant associates, arid the conditions 

 under which it is poisonous to livestock is essential. 



5 Beath, O. A., Draize, J. H. Eppson, H. F., Gilbert, C. S., and McCreary, O. C. CERTAIN 



POISONOUS PLANTS OF WYOMING ACTIVATED BY SELENIUM AND THEIR ASSOCIATION WITH 



RESPECT TO SOIL TYPES. Jour. Amer. Pharm. Assoc. 23(2) : 94-97. 1934. 



a Hurd-Karrer, A. M. SELENIUM INJURY TO WHEAT PLANTS AND ITS INHIBITION BY 

 SULPHUR. Jour. Agr. Research [U. S] 49(4)^343-357, illus. 1934. 



7 Hurd-Karrer, A. M. FACTORS AFFECTING THE ABSORPTION OF SELENIUM FROM SOILS 

 BY PLANTS. Jour. Agr. Research [U. S.] 50(5) : 413-427, illus. 1935. 



8 Byers, H. G. SELENIUM OCCURRENCE IN CERTAIN SOILS IN THE UNITED STATES WITH 

 A DISCUSSION OF RELATED TOPICS. U. S. Dept. Agr. Tech. Bull. 482, 48 pp., illus. 1935. 



