DEVELOPMENT OF THE BACTERIA. 103 



Finally, Bastian, having succeeded in obtaining 

 bacteria in liquids which he believes deprived of 

 every germ, believes in their spontaneous genera- 

 tion. The following is a resume of his experiment : 

 Normal acid urine is brought to the boiling- 

 point, then a solution of potash (in sufficient quan- 

 tity to neutralize the volume of urine employed) 

 is also brought to the boiling-point ; after cooling, 

 the two liquids are mixed, and the whole placed 

 in an oven at 50. At the end of two or three 

 days, bacteria are developed. 



Pasteur points out three causes of error in the 

 experiment of Bastian : 1. The germs may come 

 from the urine ; 2. The germs may come from the 

 solution of potash ; 3. The germs may be fur- 

 nished by the vessels employed in the experiment. 

 In support of this criticism, Pasteur has made some 

 similar experiments, guarding against these causes 

 of error, and has not obtained bacteria. 



DISSEMINATION OF BACTERIA IN AIR AND WATER. 



Air. The experiment of Pasteur for gathering 

 atmospheric germs is well known. He fixes a 

 glass tube in an aperture made in a window-blind. 

 The extremity of the tube, which communicates 

 with the open air, is closed with a plug of cotton, 

 to the other extremity is attached an aspirator. 

 When the air has filtered through the cotton for 

 some hours, this is examined, and is found to be 

 filled with germs. 



