VITALITY OF PUTREFACTIVE ORaANISMS. 167 



Last year I preserved infusion of herring perfectly 

 pellucid for months, even in a chamber so leaky that 

 the light could be seen through its chinks. I had, 

 moreover, no failure with any of the animal infusions 

 here enumerated. Last year they all remained sweet 

 and clear; this year, with far greater precaution, I 

 failed to protect any of them from putrefaction. Ee- 

 flection on these results, renders, I think, but one con- 

 clusion possible to the scientific mind. It will be loth 

 to assume that mutton, beef, pork, haddock, herring, 

 and sole had totally changed their natures, and con- 

 tracted qualities and powers in 1876 which they did 

 not possess in 1875. But if the origination of the 

 observed life be denied to the infusions themselves, 

 there is but one other source to which it could be re- 

 ferred, namely, atmospheric contamination. 



It became, indeed, more and more obvious to me that, 

 in consequence of increased vitality or virulence in the 

 contagia afloat this year, liberties in the preparation of 

 the infusions or defects in the construction of closed 

 chambers which would have been of no moment a year 

 ago were sufficient to ruin the experiments, and render 

 nugatory the usual means of sterilization. Against 

 such defects I continued to struggle. With a view to 

 stopping all chinks and crannies which might permit 

 of the entrance of contamination, I had some of the 

 chambers carefully coated with oil-silk and others 

 covered with three coatings of strong paint ; and as 

 failure had attended my efforts to procure an uninfected 

 atmosphere upstairs, I had the entire apparatus used 

 for digesting, filtering, and boiling removed to a store- 

 room at the base of the Eoyal Institution. The floor 

 of the room was of stone, and it was covered by no 

 carpet. Prior to going into it, moreover, I caused my 

 assistant to remove the clothes which he had previously 



