WHITE LOCO WEED. 89 



plants contain a poisonous principle which is harmful to domestic 

 animals. 



It should be stated also that the larvae of sheep hot flies, which are 

 frequently found in the frontal sinuses of the head, can not possibl}^ be 

 considered the cause of the nervous symptoms characteristic of the 

 loco disease, for the reason that these larvae are not found in greater 

 abundance in locoed than in health}' sheep. For the same reason the 

 presence of the common tape worm {Taenia sefi^ratci) in the small intes- 

 tines and bile duct of sheep can not be considered as the cause of the 

 locoed condition. These worms are almost universalh" present in the 

 intestines of sheep, and under ordinary conditions do not cause any 

 recognizable disturbances. The disease of sheep known as gid is not 

 to be mistaken for the loco disease and, furthermore, is not prevalent 

 in this country. No indications were found during the post-mortem 

 examinations that the walls of the stomach were aft' ected to any appre- 

 ciable extent by the action of loco weeds, although these plants were 

 invariably found in the stomach contents of such sheep. In the 

 majorit}^ of cases no apparent changes have been produced in the 

 spleen, liver, or kidneys. In some instances a slight congestion of the 

 intestines was noticed. The cerebral membranes were in all cases 

 somewhat congested. This condition is probably one of the immediate 

 physical causes of the mental excitement exhibited by locoed animals. 

 Post-mortem examinations of locoed horses disclosed the same condi- 

 tions as those found in the sheep. 



The most reliable observations on the subject of loco disease indicate 

 that it is the result of eating undue quantities of certain weeds, of 

 which a number are known. The disease may assume either an active 

 or chronic form. In the active form the animal lives but a few days, 

 while in the chronic form it may live for two or more years and man- 

 ifest the same symptoms in a milder degree. The eating of alkali may 

 bring about a perverted appetite which leads the animal to eat loco 

 weed. Otherwise alkali seems to have no connection with the loco 

 disease. 



The horse and the sheep are the animals which are most frequenth' 

 affected by loco disease. Cattle occasionally acquire the loco habit, 

 but the cases are comparativel}^ rare. In certain parts of Montana 

 the habit became so wide-spread among horses that the raising of them 

 was abandoned until the locoed animals were disposed of and other 

 horses which had not the loco habit had been imported. 



That this plant is seldom eaten by sheep, even under stress of hunger 

 (unless addicted to its use), is evident from the fact that in a case of 

 poisoning which happened near Toston, Mont., everything else, includ- 

 ing the terminal branchlets of grease wood {Chrysothamnus nauseosus) 

 and sage brush {Arteniisia tridentata)^ and even the thorny branches 

 of a wild rose, was eaten, while many flowering plants of the white 



