SPONTANEOUS GENERATION. 595 



tion, if our 940 flasks were opened on the hay-loft of the Bel Alp 85S 

 of them would become filled with organisms. The escape of the re- 

 maining 82 strengthens our case against the heterogenists, proving as 

 it does conclusively that not in the air, nor in the infusions, nor in 

 anything continuous diffused through the air, but in discrete particles 

 nourished by the infusions, we are to seek the cause of life. Our ex- 

 periment proves these particles to be in some cases so far apart on the 

 hay-loft as to permit 10 per cent, of our flasks to take in air without 

 contracting contamination. A quarter of a century ago Pasteur 

 proved the cause of " so-called spontaneous generation " to be discon- 

 tinuous. I have already referred to his observation that 12 out of 20 

 flasks opened on the plains escaped infection, while 19 out of 20 flasks 

 opened on the Mer de Glace escaped. Our own experiment at the 

 Bel Alp is a more emphatic instance of the same kind, 90 per cent, of 

 the flasks opened in the hay-loft being smitten, while not one of those 

 opened on the free mountain-ledge was attacked. The power of the 

 air as regards putrefactive infection is incessantly changing through 

 natural causes, and we are able to alter it at will. Of a number of 

 flasks opened in 1876 in the laboratory of the Royal Institution, 42 

 per cent, were smitten, while 58 per cent, escaped. In 1877 the pro- 

 portion in the same laboratory was 68 per cent, smitten to 32 intact. 

 The greater mortality, so to speak, of the infusions in 1877 was due 

 to the presence of hay which diffused its germinal dust in the labora- 

 tory air, causing it to approximate, as regards infective virulence, to 

 the air of the Alpine loft. I would ask my friend to bring his sci- 

 entific penetration to bear upon all the foregoing facts. They do not 

 prove spontaneous generation to be "impossible." My assertions, 

 however, relate not to " possibilities," but to proofs, and the experi- 

 ments just described do most distinctly prove the evidence on which 

 the heterogenist relies to be written on waste paper. 



My friend will not, I am persuaded, dispute these results; but he. 

 may be disposed to urge that other able and honorable men working 

 at the same subject have arrived at conclusions different from mine. 

 Most freely granted, but let me here recur to the remarks already 

 made in speaking of the experiments of Spallanzani, to the effect that 

 the failure of others to confirm his results by no means upsets their 

 evidence. To fix the ideas, let us suppose that my colleague comes 

 to the laboratory of the Royal Institution, repeats there my experi- 

 ments, and obtains confirmatory results; and that he then goes to 

 University or King's College, where, operating with the same in- 

 fusions, he obtains contradictory results. Will he be disposed to 

 conclude that the self-same snbstance is barren in Albemarle Street 

 and fruitful in Gower Street or the Strand? His Alpine experience 

 has already made known to him the literally infinite differences exist- 

 ing between different samples of air as regards their capacity for 

 putrefactive infection. And, possessing this knowledge, will he not 



