430 UNIVERSITY OF VIRGINIA PUBLICATIONS 



they did not form the locoweed habit until some time later. Thirty-three 

 of the sixty-five sheep were examined at autopsy, disclosing 23 cases of 

 sheep fly disease, more or less severe; 23 cases of infection with Thysanosoma 

 actinioides; a serous coagulum in the epidural spafce of the spinal canal 

 eighteen times; inflammation of the fourth stomach thirteen times; blood 

 clots in the lateral ventricles nine times, etc. Upon these findings, and re- 

 gardless of the fact that his "locoed" animals did not eat locoweed, until 

 forced to it, Marsh concluded (p. 70) that "The principal difficulty with 

 most of the animals in 1906 was the loco poison, with the effects complicated 

 by parasites." He examined more sheep the next year, however, and, 

 though he gives no details of the second group of sheep, he states; "the 

 chief trouble with most of the sheep in 1907 was caused by the parasites, 

 and that the loco had little if anything to do with their condition." He 

 then goes on to make the significant statement : 



The general appearance of the bands of sheep in 1906 and 1907 was the same, and 

 not only the author, but experienced sheepmen, declared that both bands were locoed. 

 In the majority of cases it was only by postmortem examinations that the diagnosis 

 could be confirmed. 



It is perfectly obvious that this statement by Marsh at once knocks the 

 props from under the carefully constructed and elaborate group of symp- 

 toms which he gives as characteristic of loco disease. At least in the case 

 of sheep these symptoms are not of differential value, and it is certainly im- 

 possible to detect the slightest difference between the photographs of 

 Marsh's locoed sheep, and photographs taken by Professor Chesnut of the 

 sheep studied by me. 



Marsh tries to redeem his position by adding, (p. 70) : 



If the habits of the sheep are observed there is a marked difference (between 

 locoed sheep and those suffering from parasitic disease). The sheep affected with 

 Oestrus ovis, except when they are in very bad condition, keep together like normal 

 animals, and show a preference for good food, although they may at times eat loco. 

 The locoed sheep on the other hand, are more erratic, and develop a solitary habit 

 to a greater or less extent. They show, too, a marked fondness for the locoweed. 

 At the same time, when one is dealing with a considerable number of sheep, it is a 

 matter of much difficulty to separate the locoed animals from those affected with the 

 grub in the head. 



Marsh does not even consider the difficulties of differentiating loco 

 from any other prevailing parasitic diseases of sheep except the sheep fly 

 disease. Moreover, the force of his argument is lost when it is observed 

 that his own typical locoed sheep of 1906 ate the locoweed either not at all or 

 only sparingly (p. 67-68), and when it is added that the sheep studied by 



