10 THE BEGINNINGS OF LIFE. 



infusion before it is boiled, then I have found that the 

 fluid speedily becomes turbid, owing to the appearance 

 of multitudes of Bacteria 1 . In an infusion to which 

 a fragment of cheese had been added, I have seen a 

 pellicle form in three days, which, on microscopical 

 examination, proved to be composed of an aggregation 

 of Bacteria, Vlbrtones^ and Leptothrix filaments. Again, 

 a mixture of albuminous urine and turnip-infusion has 

 rapidly become turbid in a vessel of this kind owing to 

 the presence of multitudes of Bacteria, and so also has 

 a mixture containing one-third of urine with two-thirds 

 of infusion of turnip 2 . 



Other infusions have been boiled for ten minutes in 

 a vessel with a horizontal neck two feet long, into 

 which, during ebullition, a good plug of cotton-wool 

 had been carefully pushed down for a depth of twelve 

 or fourteen inches, and cautiously increased in quantity 

 during the continuance of the ebullition. Immediately 

 after the withdrawal of the heat, the plug of wool was 

 made more dense, and the outer portion of the tube 

 was rapidly filled up with the same material to the 

 whole depth of twelve or fourteen inches. When pre- 

 served in such a vessel, a specimen of urine remained 

 unchanged ; a hay-infusion also underwent no apparent 



1 Of course germs may be in the minute fragments of cheese, just as 

 they may be in the organic infusion itself. All, however, must be killed 

 during the process of ebullition, and the subsequent results must be 

 ascribed in part to the superior molecular mobility still remaining in 

 the particles of boiled cheese. 



3 See numerous experiments recorded in Appendix C. 



