2 APPLIED BACTERIOLOGY 



in greater or lesser numbers in air, water, dust, etc. We 

 only perceive their presence under ordinary circumstances, 

 however, when the conditions are favourable to their 

 growth and development. Sometimes they give rise to a 

 putrefactive smell, or impart a colour to the body on which 

 they grow, or acquire a colour of their own. If some 

 slices of boiled vegetables, such as carrots or potatoes, be 

 exposed to the air for a few minutes, and then covered up 

 and allowed to remain for a few days in a warm place, 

 bacterial colonies will be seen to have developed, spreading 

 over the surface of the media, giving rise to characteristic 

 appearances, such as various white and coloured patches in 

 the form of little droplets, or more or less slimy masses 

 with irregular outlines. While the slices of vegetables 

 were exposed to the air, various bacterial germs fell upon 

 them, and then developed at the spots where they fell 

 into colonies, which remain isolated on the solid media. 



The history of the science of bacteriology may be said to 

 commence with the observations of Antony Leuwenhoeck, of 

 Delft, Holland, who in 1675 constructed a microscope of 

 sufficient power to demonstrate minute organisms in water, 

 putrefying fluids, saliva, etc., of a kind which up to that 

 time were quite unknown. 



A century later, namely, in 1775, the Danish investigator 

 Miiller named and described some three hundred organisms 

 occurring in the waters about Copenhagen. Miiller 

 attempted to classify these small organisms, and first used 

 the terms monas, proteus, bacillus, vibrio and spirillum. 

 The first experiments in connection with the sterilisation 

 of apparatus by heat were made by the Abbe Spallanzani, 

 about the year 1775. 



Scarcely any advance was made in our knowledge of the 

 bacteria until Ehrenberg in 1830 studied them with the 

 aid of improved instruments. The lack of culture-methods, 



