PLANT DISEASE 



To make the case the clearer, we will suppose 

 there are two farms, one having a thoroughly 

 rich soil, and the other a very poor soil, and that 

 a given number of animals were kept through 

 two or three generations on each farm. It is 

 easy to see that the animals reared on the rich 

 soil would be vigorous healthy animals, con- 

 taining the maximum of haemoglobin, fats, 

 sugars, and proteids, while the animals reared 

 on the poor soil would have become anaemic, 

 wanting in fats, sugars, and proteids, with 

 correspondingly weak constitutions. 



Taking these two lots of animals, does any 

 one doubt which would be most likely to resist 

 disease, let it be tuberculosis or other bacterial 

 disease. 



One important point in connexion with all 

 bacterial disease is that it is recognized that 

 all classes of bacteria can only live on foods 

 corresponding in chemical composition to 

 themselves, which axiom equally applies to all 

 forms of life, including man. 



With few exceptions, pathogenic bacteria 

 belong to that class of plants known as the 

 fungi. 



The distinct chemical difference between 



