130 Dr. H. C. Bastian on the Origin of Bacteria. [Jan. 30, 



son* to hold good for portions of boiled " Pasteur's solution." Air was 

 even drawn through such a fluid daily for a time, and yet it continued 

 free from Bacteria. 



Evidence of this kind has already been widely accepted as justifying 

 the conclusion that living Bacteria or their germs are either wholly absent 

 from or, at most, only very sparingly distributed through the atmo- 

 sphere. The danger of infection from the atmosphere having thus been 

 got rid of and shown to be delusive, I am now able to bring forward other 

 evidence tending to show that the first Bacteria which appear in many 

 boiled infusions (when they subsequently undergo putrefactive changes) 

 are evolved de novo in the fluids themselves. These experiments are 

 moreover so simple, and may be so easily repeated, that the evidence 

 which they are capable of supplying lies within the reach of all. 



That boiling the experimental fluid destroys the life of any Bacteria or 

 Bacteria-germs preexisting therein is now almost universally admitted ; 

 it may, moreover, be easily demonstrated. If a portion of " Pasteur's so- 

 lution " be purposely infected with living Bacteria and subsequently boiled 

 for two or three minutes, it will continue (if left in the same flask) clear for 

 an indefinite period ; whilst a similarly infected portion of the same fluid, 

 not subsequently boiled, will rapidly become turbid. Precisely similar 

 phenomena occur when we operate with the neutral fluid which I have 

 previously mentioned ; and yet M. Pasteur has ventured to assert that the 

 gsrms of Bacteria are not destroyed in neutral or slightly alkaline fluids 

 which have been merely raised to the boiling-point f . 



Even M. Pasteur, however, admits that the germs of Bacteria and other 

 allied organisms are killed in slightly acid fluids which have been boiled 

 for a few minutes ; so that there is a perfect unanimity of opinion 

 (amongst those best qualified to judge) as to the destructive effects of a 

 heat of 212° P. upon any Bacteria or Bacteria-germs which such fluids 

 may contain. 



Taking such a fluid, therefore, in the form of a strong filtered infusion 

 of turnip, we may place it after ebullition in a superheated flask with the 

 assurance that it contains no living organisms. Having ascertained also 

 by our previous experiments with the boiled saline fluids that there is 

 no danger of infection by Bacteria from the atmosphere, we may leave 

 the rather narrow mouth of the flask open, as we did in these experiments. 

 But when this is done, the previously clear turnip-infusion invariably 

 becomes turbid in one or two days (the temperature being about 70° P.), 

 owing to the presence of myriads of Bacteria. 



Thus if we take two similar flasks, one of which contains a boiled 

 " Pasteur's solution " and the other a boiled turnip-infusion, and if we 



* Thirteenth Keport of the Medical Officer of the Privy Council (1871), p. 59. 

 t How unwarrantable such a conclusion appears to be, I have elsewhere endeavoured 

 to show. See ' Beginnings of Life,' 1872, vol. i. pp. 326-333, 372-399. 



