PUTEEFACTION AND INFECTION. 57 



like that of the mutton first referred to, coagulated and 

 sank to the bottom, leaving a perfectly clear liquid 

 overhead. Six exposed tubes filled with the same infu- 

 sion were placed beside the six protected ones. 



On the 27th the exposed tubes were all turbid and 

 swarming with Bacteria. On the 29th one of the 

 tubes showed a fine green colour; three other tubes 

 showed the same colour afterwards. The vivacity of 

 the organisms was extraordinary, and their shapes 

 various. They darted rapidly to and fro across the 

 field, clashing, recoiling, and pirouetting — rendering it, 

 indeed, difficult to believe in the vegetable nature 

 which the best microscopists assign to them. 



For nearly three weeks the protected tubes remained 

 perfectly clear. To gain room, the case was subse- 

 quently shifted, and soon afterwards one of the six 

 tubes became turbid with organisms, the germs of which 

 had obviously been shaken into the tube. 



For more than a month this single infected flask 

 remained in company with the five healthy ones. The 

 air containing the gaseous products of putrefaction had 

 free access to the whole of them, but there was no spread 

 of the infection. As long as the organisms themselves 

 were kept out of the flasks, the ' sewer-gas ' developed 

 by the putrefaction had no infective power. On the 

 14th of November I infected two of the five perfectly 

 pellucid tubes with haddock-infusion which, after boil- 

 ing, had been exposed for two days to the air. On the 

 1 5th the two tubes had obviously yielded to the infec- 

 tion. On the 16th disease, if I may use the term, had 

 completely taken possession of them. Into one of them 

 only one or two drops of the turbid infusion had fallen, 

 while ten times this amount was introduced into the 

 otlier. Nevertheless on the 1 6th both appeared equally 

 Lurbid. The infection acted exactly like the virus of 



