Pathogenesis 15 



ordinary work in a regiment, were selected for expri- 

 ments. Their blood was drawn from time to time for 

 three years and was injected into healthy animals. By 

 the blood taken from a horse three years after recovery 

 two out of three became affected within the usual 

 period of incubation. In another experiment on two 

 horses, which received the blood drawn four years after 

 recovery, we found that one of them became ill after a 

 latent period of 65 days. In still another experiment on 

 two horses, which received the blood taken five years 

 after recovery, the result was negative. 



These experiments clearly show that the virus gradu- 

 ally diminishes its power and finally vanishes. 



Relation Between Patients and Their Offsprings. 



Though the infection of the disease in stable is ex- 

 tremely rare, the ralation between patients and their 

 offsprings must be of a peculiar nature. One can readily 

 notice in affected districts that young horses rarely 

 contract the disease. The following experiments were 

 undertaken to clear up this point. 



1. Blood was drawn from four foals brought forth 

 by affected mothers and was inoculated into four horses 

 (Experimental horses Nos. 443, 445, 446, 464). One was 

 affected, two showed doubtful symptoms and one gave 

 negative result. 



2. Milk of patients (30-100 c.c.) was injected into 

 three horses (Experimental horses Nos. 563, 443 566). 

 All became affected after latent periods of 24, 46 and 

 42 days, respectively. 



3. Milk of patients was given every morning inter- 

 nally to healthy stallions and colts, but no positive result 

 was obtained. 



