VITALITY OF PUTREFACTIVE ORGANISMS. 157 



filter-paper ; after which they were introduced into four 

 closed chambers of six tubes each, and then boiled for 

 five minutes. 



On the 20th of November the infusions in all the 

 chambers appeared to be as free from organisms as at 

 first. The new Heathfield and the new London hay- 

 infusions in their respective chambers had their some- 

 what turbid columns surmounted by an exceedingly 

 clear zone of liquid, due, I should consider, to the me- 

 chanical subsidence of the particles, had not subsequent 

 experience taught me to regard this appearance as a sign 

 of life. 



On the 23rd scum had begun to gather on every 

 tube of the case containing the infusion of old Heath 

 field hay. On the 30th this scum continued, but there 

 was no trace of it in any of the chambers containing 

 new Heathfield hay, new London hay, and old London 

 hay. These infusions were all somewhat turbid ; but the 

 turbidity differed very little from that exhibited when 

 the infusions were prepared. 



I spent a good deal of time over these infusions of 

 soaked hay, both with the microscope and otherwise, 

 but the recorded observations would not add materially 

 to our knowledge. I therefore dismiss them with the 

 remark that their general drift was in favour of the idea 

 that the extraordinary resistance to sterilization mani- 

 fested by the old-hay infusions is the result of hardening 

 and desiccation. The foregoing observations, however, 

 have been noted, more with the view of indicating my 

 line of thought than of claiming for them any value 

 whatever as a demonstration. 



