AIR-GERMS AND SPONTANEOUS GENERATION. 101 



erations; that it is always possible to procure, in any determined 

 place, a limited quantity of common air, having undergone no kind 

 of modification, whether physical or chemical, and nevertheless quite 

 un suited to set up any decomposing action in a liquid eminently pu- 

 trescible. The method of experimenting is very simple. Into a flask 

 of 15 to 18 cubic inches, 9 cubic inches of a liquid that has a tendency 

 to decomposition are introduced ; the neck of the flask is drawn out 

 with the lamp, leaving the point open; then the liquid is boiled till 

 the vapor escaping from the extremity has exj^elled all the air; at this 

 moment the point of the flask is closed by the lamp, by means of a 

 blowpipe, and it is allowed to grow cool. The flask then contains no 

 air; if we break off the point in any particular place, the air reenters 

 suddenly, carrying into it the germs held in suspension ; it is again 

 closed with the lamp, and kept in a stove at a temperature of 68 to 

 86 Fahr. In the generality of cases, organisms are developed ; these 

 organisms are even more varied than if the liquid were freely exposed 

 to the air, which M. Pasteur explains by saying that, in this case, the 

 germs in small number, in a limited volume of air, are not hindered in 

 their development by germs in greater number or more precocious in 

 their fecundity, which are able to occupy the space, and leave no room 

 for them. But it is especially important to notice in the results ob- 

 tained by this method, what frequently happens many times in each 

 series of trials, that the liquid continues absolutely intact, however 

 long it may have remained in the stove, as if it had been filled with 

 calcined air. This phenomenon is the more striking, and shows itself 

 in more marked proportions, when the air received into the flasks is 

 taken from a greater height. Thus, among twenty flasks opened in the 

 country, eight contained organic productions ; out of twenty opened 

 on the Jura, only five contained any ; and out of twenty flasks opened 

 at Montanvert, in a rather high wind, blowing from the deepest gorges 

 of the " Glacier des Bois," only one was affected by any change. 



Fig. 28. M. Pasteur's Flask to deprive the Air of its Germs. 



We may also draw other conclusions from this series of observa- 

 tions. Since the putrescible liquid, which had been previously boiled, 

 and which was contained in the flasks, was filled with organic produc- 



