I 8 AGRICULTURAL BACTERIOLOGY. 



their possible relations to certain diseases, and almost simul- 

 taneously they were thought of as contributing to certain gen- 



k eral changes in organic products, called fermentations. One 

 of the first real contributions to a knowledge of their signifi- 

 cance was the demonstration of the fact that certain micro- 

 scopic organisms cause an infection in dairies characterized by 

 the appearance of blue milk. Thus, it is interesting to notice 

 that, at the very beginning of the modern study of bacteria, 

 they were associated with peculiar agricultural phenomena ; 

 interesting, in view of the fact that in the next quarter of a 

 century, or more, the chief investigation, and all the interest 

 in them, centered around the question of their agency in pro- 

 ducing disease. Bacteria have suffered in reputation from the 



s fact that, at the middle of this century, they were studied by 

 microscopists chiefly from the standpoint of their agency in 

 the production of disease. It was quite early suggested, and 

 soon demonstrated, that these little plants have the power of 

 producing certain dreaded diseases, and the reputation which 

 they thus obtained has clung to them in all of the subsequent 

 years of study. This was natural enough, for mankind is always 

 particularly interested in the causes of disease, and the demon- 

 stration of their causal relations to certain dreaded diseases 

 gave to these organisms at once a wide and unenviable repu- 

 tation. The very word bacteria has become, in the minds of 

 some, almost synonymous with disease. Their relation to the 

 medical profession has been recognized, and more or less ex- 

 tended courses in the study of bacteriology have rapidly made 

 their appearance in medical schools. Health boards and sani- 

 tary commissions have recognized that their primary duty is to 

 deal with bacteria, and most of the regulations looking toward 

 preservation of the public health have been, manifestly, directed 

 toward the destruction of these organisms. 



As a result the bacteria have obtained a reputation which 

 they have not deserved. To condemn a whole group of plants 



