8 BIOLOGY AND TECHNIQUE 



With the publication of Koch's work, there began an era un- 

 usually rich in results held in leash heretofore by inadequate tech- 

 nical methods. The discovery of the typhoid bacillus in 1880, of the 

 bacillus of fowl cholera and the pneumococcus in the same year, and 

 of the tubercle bacillus in 1882, initiated a series of etiological dis- 

 coveries which, extending over not more than fifteen years, eluci- 

 dated the causation of a majority of the infectious diseases. 



Coincident with the elucidation of etiological facts began the 

 inquiry into that field which is now spoken of as the science of 

 immunity. The phenomena which accompany the development of 

 insusceptibility to bacterial infections in man and in animals, first 

 studied by Pasteur, have become the subject of innumerable re- 

 searches and have led to results of the utmost practical value. 



The problems which were encountered were first studied from a 

 purely bacteriological point of view, but their solution has shed light 

 upon biological principles of the broadest application. Investigations 

 into the properties of immune sera, while making bacteriology one of 

 the most important branches of diagnostic and therapeutic medicine, 

 have, at the same time, inseparably linked it with physiology and 

 experimental pathology. 



By the revelations of etiological research, and by the study of the 

 biological properties of pathogenic bacteria, contagion, an enemy 

 hitherto unseen and mysterious, was unmasked, and rational cam- 

 paigns of public sanitation and personal hygiene were made possible. 

 Upon the same elucidations has depended the development of modern 

 surgery a science which without asepsis and antisepsis would have 

 been doomed to remain in its medieval condition. 



Apart from its importance in the purely medical sciences, the 

 study of the bacteria has shed beneficial light, moreover, upon many 

 other fields of human activity. In their relationship to decomposi- 

 tion, the conditions of the soil, and to diseases of plants, the bacteria 

 have been found to occupy a condition of great importance in agri- 

 culture. Knowledge of bacterial and yeast ferments, furthermore, 

 has become the scientific basis of many industries, chiefly those con- 

 cerned in the production of wine, beer, and dairy products. 



The scope of bacteriology is thus a wide one, and none of its 

 various fields has, as yet, been fully explored. The future of the 

 science is rich in allurement of interest, in promise of result, and in 

 possible benefit to mankind. 



