14 



Pathogenesis. 



but it was also proved that it is retained in the blood 

 for a long time even after recovery, and causes future 

 outbreaks of the malady. In order to determine accu- 

 rately the length of the time of retention of the virus 

 in clinically recovered horses, we performed the follow- 

 ing experiments. 



Blood was drawn from 



2 horses 3 months after recovery. 



and was injected subcutaneously into 21 healthy horses. 

 All became affected except two ; one was of the number 

 which received the serum taken three months after re- 

 covery and the other of those that received the serum 

 taken thirteen months after recovery. Since the virus 

 was not detected in the blood of these two experimental 

 horses, they were killed and various viscera (liver, spleen, 

 lungs, kidneys, lymph-glands, brain, muscles, bone-marow, 

 salivary glands) were taken out of the cadavers. They 

 were again injected into healthy animals. All of them 

 manifested afterwards characteristic symptoms of the 

 disease. This undoubtedly shows that the virus was pre- 

 sent in the viscera though it was not demonstrated in 

 the blood. 



Three horses, which had completely recovered from 

 heavy attack of the disease and has been subjected to 



