376 UNIVERSITY OF VIRGINIA PUBLICATIONS 



ment of Agriculture, and in "Preliminary Catalogue of Plants Poisonous 

 to Stock, " Annual Report B. A. I. for 1898 and 1899, and by Marsh (loc. 

 cit.). 



The plants most closely connected with the disease are members of 

 the pea or bean family (Fabaceae or more broadly, Leguminosae). The 

 most widely distributed locoweeds are the Astragallus mollissimus, or 

 "woolly locoweed" or "purple locoweed," the Aragallus spicatus (Hook) 

 Rydberg, or "white locoweed," and the Aragallus lamherti. According to* 

 Marsh, who quotes Prof. C. F. Wheeler, Aragallus spicatus is identical with 

 Aragallus lamherti, but Rydberg separates them as distinct. The Aragallus 

 spicatus is the locoweed most abundant in Montana. These locoweeds are 

 found either alone or together, over much of- che area in which the disease 

 is reported. Several other closely related plants are also called locoweed. 

 Experiments with the locoweed and its extracts have yielded such in- 

 constant results that they cannot be relied upon. The more recent works 

 of Crawford, Alsberg and Marsh will be discussed later. 



Etiology. While the locoweed is generally regarded as the direct cause 

 of the disease there are many factors which are supposed to play a minor 

 part in the development of locoism. Special efforts were made to obtain 

 full information from the ranchmen as to accessory and predisposing fac- 

 tors. The following is a summary of the information obtained in this way 

 from the ranchmen. 



1. Species. Horses and sheep are most often the Adctims, cattle are 

 affected but rarely, especially in Montana (1903-1904). The Angora 

 goats of Montana are said to be quite susceptible. It is questionable 

 whether any other animals (deer, elk, etc.) ever contract the disease. 



2. Age. The statement can be obtained from most ranchmen in Mon- 

 tana that adult animals verj^ rarely if ever acquire the disease. The S3Tnp- 

 toms first appear during the first year of life or more commonlj^ during the 

 second j^ear. In the uncommon cases in which the symptoms first appear in 

 an adult it is assumed that the disease existed but was latent when the 

 animal was younger. 



S. Sex. Males and females are equally affected. 



4. Food. If animals receive a sufficient supply of nutritious food 

 (grass, alfalfa, etc.), thej- ■will rareh' if ever fall victims to the "loco habit.'' 

 The great majority of all ranclimen interviewed united in affirming the 

 close relationship between locoweed disease and an insufficient food supplj-. 

 An unusually dry season, overstocking of the ranches, or allo^ving too 

 short a time for a grazed section to recover may reduce the available suppl3' 

 of nutritious grasses, result in partial starvation of the animals and turn 

 them to the locoweed to satisfy their hunger. 



