434 UNIVERSITY OF VIRGINIA PUBLICATIONS 



the persistent, and almost exclusive use of the plant as more or less neces- 

 sary in order to produce poisoning. There seem to be exceptions even to 

 this rule, due to great individual differences among animals in their tolera- 

 tion for the plant. Many animals actually gain weight on a loco diet. 



At the present the work of Crawford, Marsh and myself seems to justify 

 opinions upon several aspects of the loco problem, provided we temporarily 

 concede that Marsh's disease results from the use of the locoweed and is 

 not due to bacteria or parasites. 



1. Some locoweeds, including Aragallus lamberti and Astragalus mollis- 

 simus, may exert a deleterious action upon live stock. Apparently not all 

 locoweeds are equally injurious. That the deleterious action is due to 

 a definite poison in the weed, as claimed by Marsh does not seem to be 

 established. 



2. There are wide individual variations in the results obtained from 

 feeding live stock upon locoweed. Some animals die; others may actually 

 gain in weight for a certain length of time. Animals may eat the weed as 

 part of their ration for years with no bad results. 



3. It requires a large amount of locoweed to produce symptoms. The 

 proportion of locoweed in the diet must be large; in fact in locoism the 

 animals seem to feed chiefly on the weed. Sheep and lambs feeding on the 

 weed as freely as they wanted it were not locoed after eating the weed A. 

 spicatus for over forty days, while the closely allied species A. lamberti &p- 

 parently produced locoism in Marsh's cattle and horses after two to five 

 months of feeding. 



4. It is an easy matter to make the animals eat locoweed. It is only 

 necessary to reduce the amount of available food, or of available fresh 

 green food, for a short time in order to start sheep eating the weed. 

 They will eat it readily — more readily than other grasses, apparently — 

 but not exclusively, as a rule. 



5. The disease described by Marsh as "loco disease" bears a certain 

 resemblance to meningo-encephalitis. 



6. There are several other diseases of live stock on the Western ranches 

 which are generally regarded as loco disease. 



7. Underfeeding or improper feeding appears to be a very important 

 factor in causing losses among the live stock. Entire flocks of sheep may be 

 underfed if the range is overstocked; or if several flocks in quick succession 

 pass over the same range; or if the season is a poor one for the growth of 

 range grass. The younger and weaker members of a band of sheep will 

 always suffer most from underfeeding, as they cannot keep in the front 

 ranks where the best food is, and they should be particularly cared for, or 



