262 STATE HORTICULTURAL SOCIETY. 



therefore look upon microbes as important factors in this grand conservative 

 process of nature. 



One of the most surprising features of this world of microscopic forms is 

 the well-established fact that each species has a specific role to perform in the 

 economy of nature; and although other allied forms may aid, or, under certain 

 conditions, approximately assume the same function, they do not carry it on 

 efficiently. 



Alcoholic fermentation is caused by the budding, or yeast fungi (saccharo- 

 mycetes), and beer, wine, and cider are the result of the functional activity of 

 three or four species, which differ somewhat in the performance of their spe- 

 cific role. Other species of the same group may, under certain conditions, pro- 

 duce alcohol, but they are not especially active in this particular form of fer- 

 mentation. 



When yeast is used in bread-making, the ordinary alcoholic ferments are' 

 concerned in the process; but in the so-called "salt-rising," a microbe 

 belonging to another group is the active agent performing a similar function. 

 The ordinary process of putrefaction, or decay, of organic substances is 

 caused by a microbe {Bacterium termo), aided by several other allied species. 

 The preservation of canned fruits is secured by destoying the life of these 

 agents of decay, by heat, and then keeping them under conditions which pre- 

 vent the access of a fresh supply of the germs of these organisms from the 

 atmosphere. 



The lactic acid of sour milk, butyric fermentation in the ripening of cheese, 

 and acetic acid are each produced by specific ferments belonging to the group 

 of microbes. The fermentation of ensilage is likewise caused in the same 

 manner and largely by the same species. 



The nitrification of soils, an essential prelude to the nutrition of plants, is 

 caused by one or more specific forms of the same group, which are, therefore, 

 of the greatest importance in agriculture. 



A specific microbe has been proved to be the cause of " pear blight," and we 

 shall undoubtedly find a similar cause of " yellows " in peaches, the " scab " of 

 potatoes, and several other diseases of plants. 



Among the communicable diseases of animals which are caused by specific 

 microbes, we may enumerate, as of especial interest to farmers, anthrax, tuber- 

 culosis, swine cholera, chicken cholera, glanders and pleuro-pneumonia, and 

 evidence is accumulating which makes it highly probable that all contagious 

 and epidemic diseases are caused and propagated by microbes. A wide field is 

 here opened for original research, as the real problems for investigation are not 

 only the fact of causation, but the life history of each specific organism must 

 be traced, together with the particular conditions which favor their develop- 

 ment, to furnish us with a rational system of prevention and cure. 



A brief historic summary of the progress of discovery will aid us in under- 

 standing the present condition of this department of science. 



The foundation for these discoveries was laid more than 200 years ago (1675), 

 when the Dutch philosopher, Leuwenhoek, by means of lenses of his own con- 

 struction, saw minute particles moving in putrid water, which are now known as 

 bacteria or microbes, and five years afterwards he made the discovery that 

 yeast was composed of minute ovoid particles, the real nature of which he was 

 unable to determine. 



About 1836 Schwann and Cagniard de la Tour independently re-discovered 

 the yeast cells of Leuwenhoek, and found them to be minute plants, which they 

 claimed were the active agents of fermentation. 



