504 Prof. J. Tyndall on the Development of [Jan. 18, 



Pursuing with scrupulous exactness the method o£ experiment devised 

 by Dr. Eoberts, and in part followed by Professor Cohn, I have found in 

 other infusions than hay an enormous resistance to sterilization. A 

 single conspicuous example will serve as an illustration. Cucumber- 

 infusion has been subjected, for intervals varying from five minutes to five 

 hours and a half, to the boiling temperature without losing its power of 

 developing life. Two days' exposure to a temperature of 90° Eahr., sub- 

 sequent to this treatment, sufiiced to develop in it swarms of Bacteria. 



The infusion which thus withstood, in one of Dr. Eoberts's " plugged 

 bulbs," the temperature of boiling water for 330 minutes, was completely 

 sterilized in three minutes by boiling it in a small flask with a narrow 

 neck, and hermetically sealing the flask during ebullition. In the case of 

 the " plugged bulbs " the observed resistance was due, not to the germs 

 of the infusion, but to those diffused in the air above it. 



I have also pursued my experiments with closed chambers, from which 

 the floating matter was removed by self-subsidence. With certain new 

 infusions introduced into this inquiry failure after failure occurred, two 

 or three days generally sufficing to fill the boiled and protected liquids 

 with Bacterial life. The vegetable infusions usually became turbid 

 throughout ; but a characteristic feature of the life developed in all infu- 

 sions during the last three months was the formation upon their surfaces 

 of a thick and deeply pitted fatty scum. Precautions far greater than 

 those found successful a year ago failed to protect these infusions from 

 contamination. 



I resorted to the mode of calcination by an incandescent platinum 

 wire, applied with such uniform success in my last inquiry. The wire 

 was brought close to its point of fusion, the period of incandescence was 

 doubled, and extraordinary care was taken to ward off infection by a ring 

 of cotton- wool. The care proved nugatory; for, in despite of it, swarming 

 life appeared in the infusions afterwards. 



I tried to reproduce the results with animal infusions obtained with 

 such ease and certainty a year ago. Some of these old infusions, highly 

 concentrated by evaporation, remain with me to the present hour ; they 

 are as clear as distilled water. But in my recent experiments, where 

 the care bestowed far exceeded that found necessary in my last inquiry, 

 the animal infusions, like the vegetable ones, fell, for the most part, into 

 putrefaction. 



With hermetically sealed flasks, properly boiled and sealed with due 

 care (I would emphasize this condition), there was no difficulty in steri- 

 lizing any of the animal infusions. 



By the scrupulous removal of every possible source of contamination 

 I was able finally to maintain some of the most refractory of the liquids 

 operated on perfectly pellucid, in closed chambers from which the floating 

 dust had disappeared by self-subsidence. 



It is to be noted that the earliest experiments of this inquiry were 



