240 Dynamic Theory. 



where the same processes of brewing and wine making are pursued. 

 The grape, which is fermented without being scalded, furnishes the yeast 

 germs, while the beer-wort, which is scalded and which is thus prevented 

 from furnishing the live germs of its own rearing, and which, on ac- 

 count of their scarcity in the air, cannot get them from that source, 

 must be supplied artificially. Schiitzenberger mentions the great 

 scarcity of yeast germs in the air, and reports that among the various 

 germs and minute organisms, caught by Pasteur in the air, he never ob- 

 tained any of the genuine, alcoholic ferment. We also have Pouchet's 

 testimony to the same effect. Besides, if these organisms < ' breed true" 

 in an unalterable line, as I infer from Tyndall's language is the theory 

 held by that school of scientists, we have to suppose that the various 

 species of alcoholic ferments, of which there are many kinds, are al- 

 ways to be found in the air. They, in many cases, affect a peculiar 

 mode of life and a particular medium for their propagation. One sort 

 is always on hand to start fermentation. Two or three others wait till 

 the first have altered the infusion before they can get in their work. 

 One kind appears to be peculiar to red wine, &c. All these must be 

 present in the air everywhere and all the time if the theory of < ' true 

 breeding" is true, and all hands agree they are scarce in the air. Prof. 

 Tyndall relates the following experiment conducted by him at the Bel 

 Alp hotel, 7,000 feet above the sea level, c He left England with sixty 

 sealed flasks of boiled infusions. Six were broken on the way and be- 

 came "muddy" with bacteria which, we infer, were packed in the 

 box with the flasks in England. Four more of the flasks were accident- 

 ally broken. The fifty remaining ones are carried to a hay loft, and 

 there the sealed ends of twenty-three of the glass flasks are snipped off, 

 1 1 Each snipping off is, of course, followed by an inrush of air into the 

 flask. We now carry our twenty-seven flasks, our pliers, and a spirit 

 lamp to a ledge overlooking the Aletsch glacier, about 200 feet above 

 the hay loft, from which ledge the mountain falls almost precipitously 

 to the northeast for about a thousand feet. A gentle wind blows to- 

 wards us from the northeast, that is, across the crests and snow fields of 

 the Oberland mountains. We are therefore bathed by air which must 

 have been for a good while out of practical contact with either animal 

 or vegetable life. " These flasks were opened here and the whole fifty 

 then hung up in the kitchen in a temperature between 50 and 90 F. 

 1 ' In three days we find twenty-one out of the twenty-three flasks opened 

 on the hay loft, invaded by organisms two only of the group remaining 

 free from them. After three weeks' exposure to precisely the same con- 

 ditions not one of the 27 flasks opened in free air had given wiy. '' The 

 shape of the necks of the flasks prevented the germs from the kitchen 

 ascending to the liquid. Prof. Tyndall draws from this the inference 



