84 PLANT DISEASE 



year after year without causing it to become 

 infected with heartwater fungus. 



At the same time, you will frequently find 

 a clean piece of country first became infected 

 shortly after a number of animals have died 

 and decayed thereon ; in fact, the liability 

 to infection depends on the chemical state of 

 the herbage. 



Some veterinary surgeons and farmers think 

 ticks are the means of spreading the disease, 

 others think not ; but from the evidence it 

 appears that it is quite as probable that ticks 

 spread this disease, as that mosquitoes spread 

 malaria. 



It must be remembered, however, that they 

 are simply a means of spreading the disease 

 and not the cause of its existence, any more 

 than the eagle is the cause of the dying stag 

 which it will hasten the death of. 



There is one fact in connexion with this 

 disease, namely, that it may be virulent on 

 one side of a fence and the sheep not suffer on 

 the other side. In cases of this kind it was 

 noticed that on the side where the sheep were 

 not suffering from this disease, it was very 

 heavily stocked, so that the herbage^was 



