MICROSCOPIC LIFE IN THE AIR. 



35 



and diminishes their nutritive properties. To obviate this, we must 

 find means to sterilize the liquids without heating them. Filtration 

 has been employed, and a number of adaptations of apparatus have 

 been devised by means of which this object is accomplished satisfac- 

 torily. 



In order to study the germs in the air, we must not only possess a 

 sensitive and wholly pure liquid, but must have means of arranging it 

 for the cultivation of the organisms, under such circumstances that 

 we may be sure it shall contain no germs except those that are de- 

 rived from the air we introduce for the experiment. MM. Chamber- 

 land and Miquel have employed simple apparatus which seem to effect 

 this purpose perfectly. 



Fig. G. Micrococcus bacilli formis (after M. Miguel). A, adult plant; B, examples of hyper- 

 trophied cells; C, chain at maturity ; D, chain destroyed. Magnified 1,0C0 diameters. 



If the experiments are made with rain-water, to ascertain the num- 

 ber of germs it collects in passing through the air, it may sometimes 

 happen that, when a determined volume of water is evenly distributed 

 in a considerable number of the cultivation-tubes, only a part of the 

 tubes will become troubled. Generally, it may be said that if the 

 water contains as the average one bacterium per cubic centimetre, 



