8 HISTORY OF MICROBIOLOGY. 



The subsequent researches on the constitution of toxins and antitoxins 

 by Ehrlich, Metchnikoff, Madsen, and others have been productive 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, and 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 or- 

 ganisms. 



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 syphilis, 

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

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

 to the ordinary staining methods. 



No one can deny that the progress of microbiology in the last forty 

 years has been extraordinary; but much still remains unknown. The 

 causes of some diseases have not been discovered. Smallpox, scarlet 

 fever, yellow fever, mumps, whooping cough, epidemic infantile paralysis, 

 hydrophobia, and others offer an inviting field to the medical micro- 

 biologist ; and the many problems of soil microbiology call for solution by 

 the agricultural microbiologist. Yet it cannot be said that the laborers 

 ' are few. 



The record of past achievements is an inspiration; and the knowledge 

 that each discovery was the result of persistent and concentrated effort, 

 may give us of the present day firmer faith and greater strength for 

 work in the broad and inviting field before us. 



