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 putrescible. 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 expelled 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 obtained 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 observations. Since the putrescible liquid, which had been previously boiled, and which was contained in the flasks, was filled with organic produc-
