ON THE OEIGIN OF LIFE. 



215 



the microscope the infusions from 19 different vases." F. Schulze* 

 then demonstrated that the sterility of the contents of these 

 vessels was not dependent upon any alteration of the air within 

 the flask, or the small quantity of air contained in it, and that 

 it was not due to any alteration brought about in the liquid by the 

 heating process. Any quantity of air, if properly purified, might 

 be sent through the flask, and no growth would follow, whilst 

 on the other hand the fluid that had been boiled, but which was 

 left exposed to the air, rapidly underwent decomposition, a process 

 accompanied by the development of micro-organisms in very 

 large numbers. Finally, Hoffmann and Pasteur,t independently 

 of each other, demonstrated that it was not even necessary to 

 close the mouth of the heated vessel with cotton-wool, as had 

 been done by Schroeder and von Dusch.J It was quite sufficient to 

 draw out and bend backwards the neck of a flask in which the 

 germ-free infusion was contained, in order to ensure the continu- 

 ance of a non-putrefactive condition and the perfect freedom from 

 germs of the fluid contained within the flask. Germs, he said, 

 like all other solid particles, when not blown about by currents, 

 obey the law of gravitation and must settle down upon an upper 

 surface, so that, when the tube was bent downwards, the organisms 

 could not fall into the mouth. Pasteur was able to keep his broth 

 sterile in hermetically sealed glass bulbs. This broth was then 

 exposed to the air in crowded rooms and on mountain heights by 

 breaking the points of the bulbs and sealing them up rapidly after 

 the exposure had been made. Of thirteen vessels of broth exposed 

 in a sleeping hut, nearly all gave evidence of the growth of 

 organisms, whilst of twenty exposed on the Mer de Glace, all 

 but one remained sterile. He found that different kinds of 

 change took place. Various vessels, exposed in different places, 

 contained different oro-anisms, and he concluded that the 

 particles suspended in atmospheric air, with the germs or seeds 

 attached to them, are the exclusive origin, the necessary 

 condition, of life in infusions. 



Charles Darwin at this time failed to see how it was possible 

 to bridge the gap between the living and the non-living. His 

 closing ai'gument in The Origin of Species brings this out very 

 forcibly : " There is a [simple] grandeur in this " (the evolu- 



Gilbert's Annalen de Pliys. u. Chemie^ Bd. xxxix, 1836, p. 836. 



t Hotfmann, Botaa. Zeitung, 1860 ; Pasteur, Gompt. rend. Acad. Sci., 

 Paris, t. 50 (1860), p. 306. 



I Ann. der Chemie u. F/iarm., Bd. Ixxxix, 1854 ; Jo urn. f. Pract. Chemie^ 

 Bd. Ixi, 1854. 



