574 FRAGMENTS OF SCIENCE. 



power, nothing is seen in the muddy liquid; but regarded 

 with a magnifying power of a thousand diameters or so, 

 what an astonishing appearance does it present! Leeuwen- 

 lioek estimated the population of a single drop of stagnant 

 water at 500,000,000: probably the population of a drop of 

 our turbid infusion would be this many times multiplied. 

 The field of the microscope is crowded with organisms, 

 some wabbling slowly, others shooting rapidly across the 

 microscropic field. They dart hither and thither like a 

 rain of minute projectiles; they pirouette and spin so 

 quickly round, that the retention of the retinal impression 

 transforms the little living rod into a twirling wheel. And 

 yet the most celebrated naturalists tell us they are vege- 

 tables. Prom the rod-like shape which they so frequently 

 assume, these organisms are called "bacteria " a term, be 

 it here remarked, which covers organisms of very diverse 

 kinds. 



Has this multitudinous life been spontaneously generated 

 in these six flasks, or is it the progeny of living germinal 

 matter carried into the flasks by the entering air? If the 

 infusions have a self -generative power, how are the sterility 

 and consequent clearness of the fifty-four uninjured flasks 

 to be accounted for? My colleague may urge and fairly 

 urge that the assumption of germinal matter is by no 

 means necessary; that the air itself may be the one thing 

 needed to wake up the dormant infusions. We will 

 examine this point immediately. But meanwhile I would 

 remind him that I am working on the exact lines laid 

 down by our most conspicuous heterogenist. He distinctly 

 affirms that the withdrawal of the atmospheric pressure 

 above the infusion favors the production of organisms; 

 and he accounts for their absence in tins of preserved 

 meat, fruit, and vegetables, by the hypothesis that fermen- 

 tation has begun in such tins, that gases have been gener- 

 ated, the pressure of which has stifled the incipient life and 

 stopped its further development.* This is the new theory 

 of preserved meats. Had its author pierced a tin of pre- 

 served meat, fruit, or vegetable under water with the view 

 of testing its truth, he would have found it erroneous. In 

 well-preserved tins he would have found, not an outrush of 

 gas, but an inrush of water. I have noticed this recently 



* Beginnings of Life, vol. i., p. 418. 



