78 PASTORAL AND AGRICULTURAL BOTANY 



the animal stepping high (Fig. 32) in approaching a stone; or a rut in the 

 road, and shies at imaginary objects (Fig. 34). As the disease progresses, 

 the animal seeks solitude, rearing up if approached. The jaws have a 

 stiff motion in eating, or drinking. The animal loses flesh, its coat be- 

 comes rough, it ceases to eat and soon dies. The symptoms of locoed cat- 

 tle are similar to those of locoed horses. There is the same lack of mus- 

 cular control, a violently shaking head, frantic running into obstructions. 

 A locoed animal is almost impossible to drive, as it is likely to run into the 

 driver, and in the opposite direction. Locoed cattle have staring eyes, 

 rough coats and gradually lose flesh. They go to water less and less fre- 

 quently and eventually die of starvation. 



The symptoms of poisoning in sheep are not so marked as with horses 

 and cattle. Locoed sheep are generally more weak, stumbling, falling and 

 rising again with difficulty. Post-mortem examinations show accumula- 

 tions of coagulated serum in a gelatinous form in various parts of the body 

 especially about the heart and spinal column. The nervous system in 

 locoed animals is more richly supplied with blood than in normal animals. 



Cause of Locoism. The specific cause of poisoning by loco weeds was 

 sought early in the presence of some toxic substance, in the plants, but 

 chemical analysis failed to reveal such. Recourse was then made to the 

 presence of tapeworms in the alimentary tract of various animals, but 

 these can hardly be the real cause of the characteristic symptoms of 

 locoism. Dr. Albert C. Crawford from his laboratory work concludes; 

 "The symptoms in stock on the range can be reproduced in rabbits by 

 feeding extracts of certain loco plants. It is the inorganic constituents, 

 especially barium, which are responsible for this poisonous action. There 

 is a close analogy between the clinical symptoms and pathological find- 

 ings 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 develop 

 analogous to those reported on the ranges." Marsh dismisses the previ- 

 ously suggested causes of the disease, other than the plants themselves, 

 as having no reasonable basis as to render them tenable. The adminis- 

 tration of sulphates, especially epsom salts to form the insoluble barium 

 sulphate, is suggested by the above discovery of the inorganic cause of 

 the loco disease. The dose used in experiments with mature cattle was 

 about one pound given in the form of a drench. For horses, the dose 

 should be about 8 ounces and for full-grown sheep 4 ounces. To improve 



