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PAKT VIII. 



METHODS OF INVESTIGATING BACTERIA. 



I do not propose in the present work to give at all a 

 complete description of the various methods of bacterio- 

 logical investigation ; such an attempt would very much 

 increase its size, and is so much the less necessary as 

 very thorough descriptions of bacteriological methods 

 have been given by Hueppe, and also in a recent work by 

 Huber and Becker (Leipzig, Vogel, 1886). 



In the following pages I shall only put together the 

 most important methods for the microscopical examina- 

 tion of bacteria, for their cultivation, and for their 

 demonstration in air, water, and soil. 



I. Microscopical Examination of the Lower Fungi. 



We can examine microscopically a great variety of Methods of 

 materials, such as fluid and solid substances, nutritive ^a^S? 

 materials, dust, earth, animal and vegetable organs and of bactena - 

 juices, fungus colonies, &c. In doing this we must 

 always remember that these lowly organisms are con- 

 stantly present in all our surroundings, and that in order 

 to demonstrate the presence of the fungi in any one of 

 these materials care must be taken to prevent the 

 accidental introduction of fungi into the preparation 

 from the surroundings. All instruments, glasses, re- Apparatus, 

 agents, &c., must therefore be free from organisms, and 

 this is best attained in the case of the instruments and 

 glasses by exposing them for a short time to a tempera- 

 ture of at least 150 C., or, still better in many cases, by 

 placing them in a solution of corrosive sublimate 1 to 

 2,000. 



