20 PLANT DISEASE 



the blood was always abnormal, either being 

 much darker or lighter than normal blood, 

 and in every case more or less non-coaguable. 

 In some cases of disease the blood has been so 

 thin as to run into the soil like water, which a 

 normal bright red blood could not do, as it 

 would coagulate on the surface. Such normal 

 blood contains a given percentage of nitrogen, 

 iron, phosphoric acid and potash, while the 

 blood of animals suffering from the class of 

 diseases known as fevers is always more or less 

 deficient in these constituents ; and it will be 

 found that the more virulent the disease, the 

 greater the deficiency. 



It can be taken as an axiom that in all 

 fevers the active agent is a bacterium, which 

 is another name for one of the class of plants 

 known as fungi. It is thought by many that 

 it is the fungus that causes the chemical de- 

 ficiency, while others say there must be a 

 deficiency before the fungus can start its 

 growth. I shall try to show that the first 

 position is untenable. Some say that while 

 the bacteria could not consume the iron, they 

 might act on the blood chemically, so that the 

 iron would escape from the system. 



