Modes op iNrECTioN. 25 



were kept together for four months. One (Experiment- 

 al horse No. 475) became ill after six months, and the 

 other remained perfectly healthy. 



From these experiments it may be concluded that 

 the disease can be propagated among the horses simply 

 by living together without the aid of insects, provided 

 the place be highly infested. But this mode of infection 

 is very weak and cannot be compared with what takes 

 place in mixed pasturing in the open air. 



The next experiment consists in keeping the pati- 

 ents and the healthy horses in separate enclosures during 

 the season of the development of insects. Thus inter- 

 course between the two sorts of animals was cut off, 

 free access of insects to the animals being allowed. 



Experiment I.— In 1911, from July 5 to October 13, 

 nine patients were kept in one enclosure to make it 

 highly infested, while in one of the neighboring, healthy 

 enclosures, four healthy animals (Experimental horses 

 Nos. 341, 342, 404, 405) were received. The latter showed 

 signs of being affected in one month and finally every 

 one of them manifested symptoms of advanced stage of 

 the disease. 



Experiment II. — In 1912 five patients were put in 

 to an enclosure ; two of them died in a short time ; one 

 fell into a heavy form of the disease ; two did not show 

 marked symptoms though strongly emaciated. In the 

 enclosure A two healthy horses (Experimental horses 

 Nos. 466, 483) were kept throughout the whole length 

 of the pasturing season. In the enclosure B four healthy 

 horses two at a time, were put in. Three of them (Ex- 

 perimental horses Nos. 477, 491, 559) manifested typical 

 symptoms ; one (Experimental horse No. 560) remained 

 unaffected. The reason why in the Experiment II. the 

 proportion of the infection was smaller than in the 



