J^RQDUCTION 



bacteriology and paves the way for the applied phases of the 

 subject. The applications of bacteriology are of particular 

 service in medicine, agriculture, either in the departments of 

 dairying, animal husbandry, horticulture, or soils ; sanitation, 

 engineering, home economics, and the commercial industries. 

 Whatever the application, however, certain fundamental 

 facts and methods must be considered, and an attempt is 

 made to present these in this general work. 



History. The existence of bacteria on the globe ante- 

 dates that of man, and yet their presence was not suspected 

 until a few centuries ago and their actual existence was not 

 demonstrated until much later. Probably the first authentic 

 observation of microorganisms was made by Kircher in 1659, 

 who demonstrated "minute living worms" in putrid meat, 

 milk, vinegar, cheese, etc., but he did not describe their form 

 or character. Anthony Van Leeuwenhoek, a Dutch natu- 

 ralist who lived from 1632 to 1723, discovered bacteria about 

 1683. Leeuwenhoek was a linen weaver by trade, but as a 

 man of some leisure he learned to grind lenses for a pastime, 

 and made them so perfectly and used them with such keen- 

 ness that he was able to see many microscopic objects for the 

 first time, and among them the bacteria. Leeuwenhoek not 

 only saw them, but he accurately described them and made 

 drawings of them as well. In a letter to the Royal Society 

 of London in 1683 he said: "I saw with wonder that my 

 material contained many tiny animals which moved about 

 in a most amusing fashion; the largest of these (A, Fig. i) 



