8 BIOLOGY AND TECHNIQUE 



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 researches and have led to 

 results of the utmost practical value. 



The problems which were encountered were hrst 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 campaigns 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 decomposition, the 

 conditions of the soil, and to diseases of plants, the bacteria have been 

 found to occupy a position of great importance in agriculture. Knowl- 

 edge of bacterial and yeast ferments, furthermore, has become the scien- 

 tific basis of many industries, chiefly those concerned 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. 



