HISTORY OF MICROBIOLOGY. 7 



nated sheep died; and the twenty-five vaccinated ones remained healthy 

 and in the same state as the ten control animals. This convincing experi- 

 ment was followed by others ; and, in the twenty-five years immediately 

 following the introduction of the method, more than ten million animals 

 were vaccinated in France alone, with excellent results. In 1885, as the 

 result of much animal experimentation, Pasteur related to the Academy 

 of Sciences his discovery of a method of vaccination against rabies, or 

 hydrophobia; and six months after the successful treatment of the first 

 case, 350 persons bitten by rabid dogs were vaccinated. An institute for 

 the preparation of vaccines was built by public subscription and named 

 the Pasteur Institute; and since that date more than thirty similar estab- 

 lishments have been founded in different parts of the world. 



This eighth decade, so pregnant with discoveries of the utmost im- 

 portance to medicine and surgery, was also notable for its discoveries in 

 agricultural bacteriology. The honor of having been the first to work out 

 the causal relation between a specific microbe and a plant disease belongs 

 to Burrill, who discovered the organism of Fire or Pear Blight; and in 1883 

 to 1888 Wakker discovered the bacillus which produces the "yellows" of 

 the hyacinth, a disease of considerable economic importance in Holland. 

 To Beyerinck, Hellriegel, and Wilfarth we owe our earlier knowledge 

 of the development and morphology of the nitrogen-fixing organism which 

 produces the nodules or tubercles on the roots of legumes. In 1888 

 Winogradsky isolated from soils nitrifying microbes which grew in a 

 medium devoid of all traces of organic matter. During this period, 

 Hansen's investigations along the line of the fermentation industry were 

 most important. He devised methods for securing pure cultures of yeasts 

 starting from a single cell, showed that yeasts _ produced diseases in beer, 

 and established the method of identifying yeasts by observing their micro- 

 scopic appearance, the formation of ascospores, and the production of films. 



The tenth decade of the nineteenth century was almost as prolific in 

 discovery as the ninth. In 1890 Behring discovered the antitoxin for 

 diphtheria, as a result of the pioneer work on toxins by Roux and Yersin. 

 Five years later, this serum came into general use as a curative; and the 

 efficiency of the treatment is shown by a comparison of the death rate from 

 diphtheria before and after the introduction of the antitoxin. The average 

 annual death rate from diphtheria in eight large cities, during the period 

 1885-1894, was 9.74 per 10,000 of the population before the use of anti- 

 toxin; and during the antitoxin period of 1895-1904 it was 4.29. 



