12 PLANT DISEASE 



into an animal does not necessarily cause disease. 

 Were it otherwise it is difficult to see how the 

 higher organisms could escape at all. Some- 

 thing must therefore be placed to the action of 

 the tissues of the host which, when healthy, 

 can ' resist ' the attempts of bacteria to settle, 

 grow, and multiply with fatal effect." 



" Pasteur has shown that anthrax bacillus 

 cultivated in chicken broth, with plenty of 

 oxygen, and at a temperature of 42-436. lost its 

 virulence after a few generations, and ceased 

 to kill even a mouse. This has been con- 

 firmed by others " (see Encyclopaedia Britan- 

 nica, vol. xxi. p. 400). 



In tuberculosis again, it is universally recog- 

 nized that oxygen is very beneficial, but the 

 fact that thousands of cattle living in the open 

 air suffer from it shows that it is not sufficient 

 that the oxygen should enter the lungs, but 

 that it is necessary that it should be absorbed 

 into the system, which can only be accomplished 

 by the action of a normal haemoglobin. 



It is clear from the above that in certain 

 diseases at any rate, and as I think in most, the 

 animal having a normal haemoglobin is more 



