406 UNIVEESITY OF VIRGINIA PUBLICATIONS 



weed without manifesting any ssnnptoms that could be attributed to the 

 action of the weed. 



When the experiment was interrupted, it might have been expected that 

 the animals would show symptoms from being suddenly deprived of the 

 weed, just as morphine habitues, alcoholics and tobacco smokers show 

 symptoms when suddenly deprived of their drugs. This did not occur with 

 the sheep, and they were carefully watched in order to observe any manifes- 

 tations of this nature. On the contrary, the improvement in the condition, 

 of the sheep when their diet was increased was almost immediate and re- 

 sembled nothing so much as the improvement which takes place in a half 

 starved animal when it is placed upon a proper diet. 



When the experiment was resumed, another interesting observation 

 was made: The animals were turned back upon the abundant loco fields 

 after an abstinence from the weed lasting for eight days. It is a common 

 impression that drug users exhibit symptoms when they are suddenly put 

 upon full doses of their drugs after abstinence. This did not occur with the 

 sheep. They were turned into the corrals with loco about an hour after 

 they had finished eating the alfalfa hay which had been given them. They 

 had left some alfalfa hay uneaten, and were lying around in the corners of 

 the corrals. When turned into the corral with fresh forage, they at once 

 began to graze, eating loco and other plants for an hour and a half. At no 

 time did any animal exhibit a single symptom that could be attributed to 

 the weed. 



Another very interesting observation was made during this infection 

 with the sheep fly. The animals badly infected with these parasites pre- 

 sented the most typical pictures of loco disease. On turning to the descrip- 

 tion of sheep fly disease, the Western rancher might well think that the 

 writer of the book was confused and was writing a description of the loco- 

 weed disease. It must be remembered, however, that sheep fly disease 

 occurs all over the world, and the symptoms have been described as char- 

 acteristic for animals which are entirely beyond the reach of locoweed. 



The following description taken from Neumann's Parasites and Parasitic 

 Diseases of the Domesticated Animals, 1903, pp. 568-570, is inserted in order 

 to make this clear: 



"it (the sheep fly) hides in holes and crevices in the walls of the sheepfolds, which it 

 leaves when coupling time has arrived and the temperature is suflSciently high. It then 

 flies in a lively manner to greater elevations',, and rests on rocks warmed by the sun. 

 The fecundated female now goes in search of flocks of sheep, which are afraid of its 

 approach, and to avoid it lie down, bury their noses in the dust between their fore- 

 feet, or are huddled together with their heads down. According to Bracy-Clark, 



