TYNDALL ON SPONTANEOUS GENERATION. 679 



with their liquids as clear as filtered drinking \Yater. In six flasks, how- 

 ever, the infusion is found muddy. On examination, it is discovered that 

 every one of these has its fragile end broken off in the transit from London. 

 Air has entered the flasks, and muddiness is the result. Examined with a 

 pocket-lens, or even with a microscope of insuflScient power, nothing is 

 seen in the muddy liquid ; but regarded with a magnifying power of a thou- 

 sand diameters* what an astonishing appearance does it present ? Leeu- 

 wenhoek 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 ten times multiplied. The field of the microscope is crowded with 

 organisms, some "wobbling" slowly, others shooting rapidly across the 

 microscopic field. They dart hither and thither like a rain of minute pro- 

 jectiles; they pirouette and spin so quickly round that the retention of the 

 retinal impression transforms the little living rod into a twirling reel. And 

 yet the most celebrated naturalists tell us that they are vegetables. Has 

 this multitudinous life been spontaneously generated in these six flasks, or 

 is it the progeny of living germinal matter carried into the flask by the en- 

 tering air ? If the infusions have a self-generative power, how are the ste- 

 rility and consequent clearness of the fifty-four uninjured flasks to be 

 accounted for? It has been affirmed in support of the theory of heterogeny 

 that the vacuum above the infusion is favorable to the production of organ- 

 isms, and their absence from tins of preserved meats, fruit and vegetables 

 is accounted for by the hypothesis that fermentation has begun in such 

 tins, that gases have been generated, the pressure of which has stifled the 

 incipient life and stopped its further development. But in well preserved 

 tins. Dr. Tyndall has invariably found, not an outrush of gas, but an inrush 

 of water, if they, were perforated under water. He has noticed this in mod- 

 ern tins, and in tins which have been perfectly good for sixty-three j^earg. 

 On the other hand, he has exposed the organisms to pressure of gases 

 without killing them. The fifty-four pellucid flasks declare against the 

 heterogenist. The flasks are next exposed to a warm Alpine sun by day, 

 and at night suspended in a warm kitchen. Four of them have been acci- 

 dentall}^ broken, but at the end of a month the fifty remaining flasks are 

 found as clear as at the commencement. There is no sign of putrefaction 

 or of life in any of them. 



These flasks are divided into two groups of twenty-three and twenty - 

 seven respectively. The question now is whether the admission of air can 

 liberate any generative energy in the infusions. The flasks are carried to 

 a hay-loft and the ends snipped off from the group of twenty-three. The 

 twenty-seven flasks are borne to a ledge 200 feet higher, from which the 

 mountain falls away precipitously to the northeast for about 1,000 feet. A 

 gentle wind blows toward it from the northeast, across the crests and snow 

 fields of the Bernese Oberland. The spot is, therefore, bathed in air which 

 must have been for a good while out of contact with either animal or vege- 

 table life. Standing carefully to the leeward of the flasks, for no dust or 



