304 ANNUAL OP SCIENTIFIC DISCOVERY. 



organic germ has been previously destroyed, and to which the air has only 

 access after passing through concentrated sulphuric acid, or through a laby- 

 rinth of porccl.iin fragments at red-heat. Xay, M. Pouchet goes further. 

 Feeling the difficulty of satisfying his opponents that the atmospheric air 

 really contained no germs, he determined on substituting artificial air. This 

 he did in conjunction with a chemist, M. Hougeau. Artificial air, as the 

 reader knows, is simply a mixture of twenty-one parts of oxygen gas with 

 seventy-nine parts of nitrogen gas. This air Avas introduced into a flask 

 containing an infusion of hay, the hay having previously been subjected for 

 twenty minutes to a heat of one hundred degrees Centigrade (two hundred 

 and twelve degrees Fahrenheit), a temperature which would destroy every 

 germ. He thus guarded against the presence of any germs, or animalcules, 

 in the infusion, or in the air. The whole was then hermetically sealed, so 

 that no other air could gain access. In spite of these precautions, crypto- 

 gamic plants and animalcules appeared in the infusion. M. Pouchet re- 

 peated the experiment with pure oxygen gas, instead of air; and with simi- 

 lar results. 



In presence of such statements as these, only two courses were open to 

 the antagonists of spontaneous generation. They could deny or disprove 

 the facts; or they could argue that the precautions taken were not suffi- 

 ciently rigorous to exclude the presence of germs. I have already said how 

 difficult it is for the modern physiologist to admit spontaneous generation, 

 and the reader will therefore be prepared to hear that M. Pouchet has roused 

 immense opposition; but the opponents have not disputed his facts; one 

 and all, they accept the statements as he makes them, and, by criticism and 

 counter-statement, endeavor to show that spontaneous genei-ation is just as 

 impossible as ever. These criticisms, and M. Pouchet's replies, may here 

 le grouped in order, and with all possible brevity. 



Milne-Edwards objected to the conclusions of M. Pouchet, saying: There 

 is no proof that the hay itself had been subjected to the temperature of 

 one hundred degrees Cent, (or the boiling-point of water), it being very 

 probable that although the furnace was at that heat, the hay, which was in 

 a glass vessel and surrounded with air at rest, was not at anything like that 

 temperature. 



To this M. Pouchet replied, that he and M. Hougeau ascertained that the 

 hay was at the temperature of one hundred degrees, before they proceeded 

 in their experiments. 



Milne-Edwards is ready to grant that the temperature may have been 

 reached, but argues that even that would not suffice for the destruction of 

 all the germs, if they were perfectly dry. He refers to the observations of 

 M. Doyere, which prove that the Tardigrada (" water-bears," microscopic 

 animals common in stagnant water), when thoroughly desiccated, preserve 

 their power of reviving even after having been subjected to a temperature 

 of one hundred and forty degrees Centigrade (three hundred and sixteen 

 degrees Fahrenheit). If, therefore, animals of so complex a structure as 

 these water-spiders can resist the action of so high a temperature, there is 

 no reason for supposing that the germs of the simpler animalcules would be 

 destroyed by it. Xot content with this argument, which is sufficiently forci- 

 ble, Mine-Edwards narrates an experiment of his own, which is very simi- 

 lar, both in method and results, to one I have performed. Unhappily, it is an 

 experiment the value of which is either destroyed by the argument just ad- 

 duced, or else it destroys the argument. It is this : In two tubes a little water 



