PEOGRESS OF MICROSCOPICAL SCIENCE. 197 



porting the life of bacteria, for by inoculating it witb a drop of ordi- 

 nary distilled water it at once becomes pregnant. Hence I conclude, 

 not that spontaneous generation is impossible, but that the i)articular 

 experiment in question is not an instance of it, and that no argument 

 founded on it in favour of the doctrine is of the slightest value. 



It is unnecessary for me to occuj)y your space by at any length 

 adverting to the side questions raised by Dr. Bastiau in the other 

 paragraphs of his letter. 



In examining the liquids within a few days after heating rather 

 than later, I followed his own method. 



I made no attempt to determine the temperature of ebullition in 

 flasks with capillary orifices, because I know of no method by which it 

 could be done accurately. Besides, it was not required for my purpose. 



I employed the word " chance " in its ordinary sense. In the sentence 

 to which Dr. Bastian refers I explained that, although there may be 

 a limit of temperature at which a liquid, before possessing the power 

 of breeding bacteria, is deprived of that power, experiments such as 

 mine are insufiicient to define that limit. As regards the turnip-cheese 

 liquid it has been shown that between the temperatures of 100° and 

 102° C, the probability of pregnancy diminishes rapidly as the tem- 

 perature increases. It is not as yet possible to say at what point the 

 probability vanishes. 



Then comes Dr. Bastian's reply, which says that " Dr. Sanderson 

 expresses some surjjrise that I was gratified by the facts recorded in 

 his jorevious letter. My reasons were these. Dr. Sanderson's experi- 

 ments in the eight successive cases in which he employed the tem- 

 perature of 100° C. for twenty minutes were entirely confirmatory of 

 my own, and were, moreover, so conducted as to refute the objections 

 which have been urged by Dr. Wm. Roberts and others." 



As to the bearing of Dr. Sanderson's experiments with higher 

 temperatures and more prolonged periods of exposure to heat upon 

 the general question of the independent origin of living matter, I 

 wholly dissent from his now expressed conclusions, for the following 

 reasons : — 



In the first place his fluids were not kept sufiiciently long before 

 they were submitted to microscopical examination. Dr. Sanderson is 

 quite mistaken in supiDosing that in examining his liqxiids within 3-6 

 days after their preparation he was following my method — more espe- 

 cially in cases such as these where the fluids have been ex2)osed to 

 temperatures higher than usual, or to 100° C. for upwards of twenty 

 minutes. Three to six weeks have often elapsed before I thought it 

 judicious to open my flasks.* In oj)ening all his flasks at the end of 

 3-6 days. Dr. Sanderson lost the opportunity of watching the changes 

 which might have ensued later in many of his experimental fluids — 

 and hence lost his right to draw any conclusions from these abortive 

 trials. 



Secondly, these experiments are open to another objection. Dr. 

 Sanderson concludes from them that exposure to a temperature of 

 101° C. almost always arrests the tendency to fermentation in his 

 * See ' Begumiugs of Life,' vol. i., p. 355, p. 441, auJ Append. C. 



