CHAPTER X. 



flight. 



HAVING discussed three of the causes that are at the 

 bottom of the general complaint of declining orchards 

 everywhere throughout the eastern half of the United 

 States, we now come to the fourth ; that is, disease. 



In human physiology, the last few years of scientific 

 research have developed the most wonderful discoveries. 

 Mysteries that were dark, and problems hidden for ages, are 

 now made as clear as day by the germ theory of disease in the 

 human system. And not only are diseases accounted for and 

 explained on this theory and by actual observations under the 

 microscope, but also the commonest functions of our bodies, 

 such as digestion, and other useful fermentations, as those of 

 yeast, wine, beer, the nitrification of the soil, are all due to 

 the incubation and multiplication of millions of those myste- 

 rious little spores, germs, microbes, bacilli, bacteria, etc., 

 good, bad and indifferent, that swarm everywhere in the earth, 

 the air, our bodies, and everything on the earth. These facts 

 are, of course, known and admitted everywhere, and science 

 has been and is now devoting all its energies to the discovery 

 of the laws and conditions which regulate and govern these 

 infinitesimal creatures in their propagation and relation to 

 disease in the human system. But, while the majority of 

 scientists have turned their attention to man and his bacterial 

 friends and enemies, Professors Burrill, Galloway and others 

 are giving their best endeavors to the study and elucidation 

 of the subject in connection with the diseases of plants, 

 especially the various forms of blight of the apple and pear, 

 and the yellows in the peach. That these diseases, as well as 

 root-rot and black-knot of the peach and plum, are due to the 

 presence in the sap of minute organisms known as bacteria, 

 seems clearly established, and that probably epidemics, as 



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