vui. B, « Boynton: Rinderpest Blood in Water Leech 519 



elapse before ulcers would appear. Therefore, it was probable 

 that this animal had nearly recovered and might not have been 

 capable of spreading the disease. 



Experiment 35. — On May 8, 1913, the leech, which on May 3 

 had fed on the carabao showing ulcers in its mouth, was caused 

 to disgorge in physiological salt solution. This mixture of blood 

 and salt solution was injected subcutaneously into bull 3573. The 

 animal showed no ill effects from the injection. It was later 

 proved susceptible to rinderpest. 



On May 4, 1913, in Ilocos Sur, one leech was allowed to feed 

 on a carabao which was recovering from an attack of rinderpest. 

 The leech was placed in water and brought to the laboratory. 

 This animal had presented some symptoms of rinderpest ; as, for 

 instance, a discharge from its eyes and nose and a mild diarrhoea. 

 At the time the leech was allowed to feed, these symptoms had 

 practically disappeared. 



Experiment 36. — On May 8, 1913, the leech, which had been 

 allowed to feed on the recovering animal on May 4, was caused to 

 disgorge by placing it in salt solution. This mixture of blood and 

 salt solution was injected subcutaneously into bull 3574. The 

 animal showed no ill effects from his injection. It was proved 

 to be susceptible to rinderpest at a later date. 



CONCLUSIONS 



1. From the results obtained in experiment 22 and others it 

 is proved that the large water leech (Hirudo boyntoni Wharton) 

 can retain the virus of rinderpest alive in its body for at least 

 twenty-five days and in a virulent condition. 



2. From experiment 4 it is shown that water in which leeches 

 have disgorged blood by mechanical stimulation or other means, 

 after holding it for a period of five days, will cause rinderpest 

 when drunk by a susceptible animal. 



3. The result obtained in experiment 5 proves that leeches, 

 which have died from mechanical or other cause, after holding 

 virulent blood for five days, are able to transmit the disease when 

 the blood is ingested by a susceptible animal. 



4. From experiments 4 and 11 it is shown that an animal may 

 have an incubation period of ten days after being infected with 

 material which has been held by a leech. 



5. Experiment 16 shows that an animal may develop a very 

 mild type of the disease when infected from blood that has been 

 held in a leech for several days. Under such conditions an ani- 

 mal experiencing a mild attack may transmit a virulent and fatal 



