8 HISTORY OF MICROBIOLOGY 



identifying yeasts by observing their microscopic appearance, the for- 

 mation 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 cura- 

 tive agent; 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 1885-94, was 9.74 per 10,000 of 

 the population before the use of antitoxin; and during the antitoxin 

 period of 1895-1904 it was 4.29. 



The subsequent researches on the constitution of toxins and anti- 

 toxins by Ehrlich, MetchnikofI, Madsen, and others have been pro- 

 ductive of a better understanding of the problems of immunity. 



In 1892 Pfeiffer discovered the organism of influenza or grippe; and 

 in 1894 Yersin and Kitasato independently discovered the bacterium of 

 bubonic plague. 



The now well-known serum diagnosis of typhoid fever, whereby 

 living and motile typhoid bacilli are clumped and lose their motility 

 when placed in the diluted serum of a patient suffering from the 

 fever, was due to the work of Gruber and Durham, and the exploitation 

 of the method by Widal dates from 1896. 



In 1898, Shiga discovered the bacterium of dysentery, and the pos- 

 sible cause of pleuro-pneumonia in cattle was found by Nocard. This 

 latter organism was so minute as to be at the extreme limit of micro- 

 scopic definition, and suggested that other well-known diseases, such as 

 foot-and-mouth disease, are probably caused by ultra-microscopic 

 organisms. 



This year, Ronald Ross worked out the relation between man, the 

 mosquito, and the malarial parasite a discovery which at once sug- 

 gested the best means of controlling the disease. 



In 1905, Schaudinn definitely established the causal agent of syphi- 

 lis, a spirochaete-shaped organism, which he named Treponema pallidum, 

 and which had escaped earlier discovery on account of its being refractory 

 to the ordinary staining methods. 



In the last decade, our knowledge of certain communicable diseases 

 has been extended considerably. Preventive and prophylactic measures 



