CHAPTER II 

 THE DEVELOPMENT OF BACTERIOLOGY 



Discovery of bacteria. The study of bacteria is one of 

 the most recent developments of biologic science. The facts 

 that had been gathered concerning the bacteria were not 

 grouped into an independent phase of biology until about 

 1880. It was not until 1882 that the new science received 

 its name, bacteriology. The bacteria had first been seen 

 in 1683 by Leeuwenhoek. Apparently he was the first to 

 use an instrument of sufficient magnifying power in such a 

 way as to make the bacteria visible. 



The compound microscope was first made by Johannes 

 Janssen and his son, in Holland, in 1590. The objects to 

 be examined by such an instrument were illuminated by 

 light coming from above, and reflected from the surface 

 of the object into the lens of the microscope, and thence to 

 the observer's eye. With such an arrangement the bacteria 

 could not be seen. Leeuwenhoek used a simple microscope 

 in his work, of lower power than others had employed. He, 

 however, examined his objects by placing them between the 

 source of light and his lens: he used transmitted light, or 

 the kind one uses when he wishes to determine the free- 

 dom of a liquid from suspended matter, and places it be- 

 tween his eye and the window. The solid objects refract 

 the rays of light, and thus their presence in the liquid is 

 made evident to the eye. This simple modification of his 

 microscope made Leeuwenhoek the discoverer of many mi- 

 croscopic objects, among them the yeasts and the bacteria. 

 He is frequently called the father of microscopy. 



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