SPONTANEOUS GENERATION, SO CALLED. 263 



answer to this question lies in the experimental test. When 

 infusoria make their appearance in solutions that have been 

 exposed to heat and protected from the entrance of germs, it 

 is said that the heat has not been sufficiently high or the ex- 

 posure has been of too short duration. When infusoria do 

 not appear, the conditions are assumed to have been fulfilled. 

 This mode of reasoning assumes the fact, from the beginning, 

 that there is no such thing as spontaneous generation. Sup- 

 pose, now, we start with the contrary assumption, that there 

 may be spontaneous generation in an organic infusion. We 

 admit to such an infusion, air, carefully purified from germs, 

 which is logically an essential experimental condition; we 

 have previously exposed the infusion to a high temperature 

 for a certain period. Under these conditions, no infusoria 

 appear. It may then be assumed that the heat has destroyed 

 the properties of the organic molecules, so that they cannot 

 come together and generate new beings. 



Under these circumstances, all that we can do is to argue 

 logically from such facts as have been positively established, 

 and to take the most reasonable view of other points, that 

 are not as yet capable of satisfactory and definite explanation. 



We shall assume that it has been demonstrated, beyond a 

 reasonable doubt, that, in organic infusions, subjected to a 

 temperature somewhat above that of boiling water, and sup- 

 plied with air that has been effectually deprived of organic 



only to air which had passed through iron tubes heated to redness, became the 

 seat of infusorial life. Exps. i.-v. 



" 3d. Similar solutions contained in flasks hermetically sealed, and then im- 

 mersed in boiling water for periods varying from a few minutes to four hours, 

 also became the seat of infusorial life. The infusoria were chiefly Vibrios, Bae- 

 teriums, and Monads. Exps. vi.-xv. 



u 4th. No ciliated infusoria, unless Monads are such, appeared in the experi- 

 ments referred to in the above conclusions. 



" 5th. No infusoria of any kind appeared if the boiling was prolonged be- 

 yond a period of five hours." 



(JEFFRIES WYMAN, Observation* and Experiments on Living Organisms in 

 Heated Water, New Haven, 1867, p. 20. From the American Journal of Science 

 and Arts, vol. xliv., September, 1867.) 



