VITALITY OF PUTEEFACTIVE ORGANISMS. 145 



described. Accordingl}^, on the 24th of October, I had 

 four groups of Cohn's tubes (twelve in a group) carefully- 

 charged with two fresh infusions of two different kinds of 

 hay. Each infusion was divided into two equal parts, one 

 of which was neutralized and the other left in its natural 

 acid condition. Twelve of the tubes were charged with 

 one of the infusions neutralized, and twelve with the 

 same infusion unneutralized. We will label this in- 

 fusion A. Twelve other tubes were charged with the 

 second infusion neutralized, and twelve with it unneu- 

 tralized. We will call this infusion B. The forty-eight 

 tubes were subsequently boiled for ten minutes in tin 

 vessels containing water deep enough nearly to submerge 

 them. Having proved by previous experiments that it 

 was dangerous if not fatal to exactness to expose the in- 

 fusions for one or two minutes to the air after their 

 removal from the water, I took the precaution of plug- 

 ging them first and removing them afterwards. 



On the 28th of October (that is to say, four days 

 after their preparation) several of the tubes containing 

 the imneutralized infusion A were faintly but distinctly 

 turbid and thinly covered with scum. The twelve 

 neutralized tubes of the same infusion were at the same 

 time perfectly clear. This retarding influence of the 

 alkali has been of frequent occurrence in this inquiry. 

 That it was simply a case of retardation was proved by 

 the fact that, on the 30th of October, the twenty-four 

 tubes, both neutral and acid, of infusion. A were tm:- 

 bid and covered with scum. 



On the same date the twelve neutralized tubes of 

 infusion B were perfectly clear and without a trace of 

 scum. Of the twelve unneutralized tubes three had 

 given way, and a fourth yielded on the 31st. Four 

 days later three of the neutralized tubes also yielded. 

 The permanent state of matters was that eight out of 



