92 THE POPULAR SCIENCE MONTHLY, 



who have entered upon it from Needham's time to the present day- 

 ought to have made use of it. 



The serious and grave difficulty, on which, during this period, all 

 discussions raised between heterogenists and panspermists have turned, 

 is so to arrange the experiments as to remove every suspicion of the 

 intervention of germs bi-ought from without, or preexisting in the 

 liquid. 



If the result is negative, if when all precautions that seem to be 

 necessary have been taken, and all causes of error have been removed, 

 there is no formation of infusoria, ft will be difficult to raise any seri- 

 ous objection to the inevitable conclusion, provided that the methods 

 employed for the purpose of eliminating the preexisting germs are not 

 of such a nature as to modify the medium, and to render it unfit for 

 the development and the nutrition of living organisms. If, on the 

 contrary, we still meet with the birth of living beings, the suspicion 

 will always revive that the experiment has been badly performed, and 

 that a contrary result would have been obtained by conducting it more 

 carefully. The heterogenists, therefore, find themselves in a more dis- 

 advantageous situation than their opponents, and, notwithstanding 

 the success which they may obtain, they will never convince them. 



We think, therefore, that it is useless to give here a detailed 

 account of their minute researches ; they must be consulted in the 

 original memoirs. A single experiment which proves, by a negative 

 result, that organic infusions, protected from germs from without, do 

 not give birth to infusoria, is icorth more, scientifically speaking, than 

 ten experiments tending to establish the contrary opinion. 



If, therefore, we pass over the details of the fundamental exjjeri- 

 ments of the heterogenists, and speak of those the results of which are 

 conformable to the ideas of the panspermists, it will not be in a spirit 

 of partiality. We are convinced that the latter are the only ones free 

 from all objections, the relative skill of the operators being disregard- 

 ed, and considered as nothing in the estimate formed. We may, how- 

 ever, say that M. Pasteur's researches may serve as a model for all 

 those who may wish to conduct investigations of this kind, whatever 

 may be the preconceived opinion by which they are guided. By their 

 precision, and the care taken to remove every source of error, they 

 leave nothing to be desired. 



As the results obtained by M. Pasteur lead him to deny spontane- 

 ous generation, his opponents must above all prove that he is mis- 

 taken, by adopting the same rigorous experimental conditions. Need- 

 ham's experiments, which led him to admit and sustain the doctrine 

 of spontaneous generation, consisted essentially in placing organic 

 substances which were capable of decomposition, in vessels hermeti- 

 cally sealed, which were subsequently submitted to a high temperature, 

 in order to destroy the preexisting germs. The work of the English 

 writer attracted great notice on account of the support of Buifon, 



