96 THE LIFE OF PASTEUR 



water, he submitted each flask to ebullition. The neck of 

 those vessels was ended off in a vertical point. Whilst the 

 liquid was still boiling, he closed, with an enameller's lamp, the 

 pointed opening through which the steam had rushed out, 

 taking with it all the air contained in the vessel. Those flasks 

 were indeed calculated to satisfy both partisans or adversaries 

 of spontaneous generation. If the extremity of the neck of one 

 of these vessels was suddenly broken, all the ambient air 

 rushed into the flask, bringing in all the suspended dusts ; the 

 bulb was closed again at once with the assistance of a jet of 

 flame. Pasteur could then carry it away and place it in a tem- 

 perature of 25-30° C, quite suitable for the development of 

 germs and mucors. 



In those series of tests some flasks showed some alteration, 

 others remained pure, according to the place where the air had 

 been admitted. During the beginning of the year 1860 Pasteur 

 broke his bulb points and enclosed ordinary air in many dif- 

 ferent places, including the cellars of the Observatory of Paris. 

 There, in that zone of an invariable temperature, the abso- 

 lutely calm air could not be compared to the air he gathered 

 in the yard of the same building. The results were also very 

 different : out of ten vessels opened in the cellar, closed again 

 and placed in the stove, only one showed any alteration ; whilst 

 eleven others, opened in the yard, all yielded organized bodies. 



In a letter to his father (June, 1860), Pasteur wrote : ' I 

 have been prevented from writing by my experiments, which 

 continue to be very curious. But it is such a wide subject that 

 I have almost too many ideas of experiments. I am still being 

 contradicted by two naturalists, M. Pouchet of Rouen and M. 

 Joly of Toulouse. But I do not waste my time in answering 

 them ; they may say what they like, truth is on my side. They 

 do not know how to experiment ; it is not an easy art ; it de- 

 mands, besides certain natural qualities, a long practice which 

 naturalists have not generally acquired nowadays." 



When the long vacation approached, Pasteur, who intended 

 to go on a voyage of experiments, laid in a store of glass flasks. 

 He wrote to Chappuis, on August 10, 1860 : " I fear from your 

 letter that you will not go to the Alps this year. . . . Besides 

 the pleasure of having you for a guide, I had hoped to utilize, 

 your love of science by offering you the modest part of curator. 

 It is by some study of air on heights afar from habitations and 

 vegetation that I want to conclude my work on so-called spon« 



