SILOS, EKSILAGE AND SILAGE. 45 



test tubes, intended to contain the liquid to be exposed 

 to the action of the moteless air. 



" The arrangement is represented in Fig. 3, where w w 

 are the side windows (through which a searching beam 

 passes from a lamp I across the case) ; p is the pipette, 

 and a, I, are the bent tubes connecting the inner and 

 outer air. The test tubes passing through the bottom 

 of the case are seen below. 



" On the 10th of September, 1875, this case was 

 closed. The passage of a concentrated beam across it 

 through its two side windows then showed the air within 

 it to be laden with floating matter. 



" On the 13th it was again examined. Before the 

 beam entered, and after it quitted the case, its track was 

 vivid in the air, but within the case it vanished. Three 

 days of quiet had sufficed to cause all the floating mat- 

 ter to be deposited on the interior surfaces, where it was 

 retained by a coating of glycerine, with which these sur- 

 faces had been purposely varnished."* 



After the air was thus purified by the subsidence of 

 the floating particles with which it was contaminated, 

 the test tubes were partly filled through the pipette, 

 with a variety of solutions that were readily acted upon 

 by the micro-organisms of putrefaction, as dilute infu- 

 sions of beef and mutton broth, urine, and of different 

 vegetables, as turnips, cucumbers, etc., and these were 

 sterilized by dipping the test tubes that project below 

 the bottom of the case, in a bath of boiling brine for 

 five minutes. It will be seen that these putrescible 

 materials in the test tubes were in immediate contact 

 with the purified air of the chamber, which freely com- 

 municated with the external atmosphere through the 

 bent tubes at the top of the case. 



Under these conditions the contents of the test tubes 

 were kept for months without undergoing any change. 



* " Floating Matter of the Air," pp. 49-51. 



