170 ORIGIN AND NATURE OF LIFE 



This paper attracted universal attention, 

 and stimulated, on the part of Pasteur, 

 four years of incessant labour, crowded with 

 ingenious experiments, all planned towards 

 one common end. He showed that sterilized 

 cultures always became infected when exposed 

 to air ; that properly filtered or sterilized air 

 never caused infection ; that Alpine air 

 almost free from germs scarcely ever produced 

 a growth of organisms ; that city air nearly 

 always produced contamination ; and that 

 in absence of added germs from without, 

 culture media remained sterile for years. 

 The sources of error in the work of his oppon- 

 ents were elucidated, and their contrary 

 results explained on such grounds. So, step 

 by step, each logically thought out, Pasteur 

 established his position. 



Passing on to the applications of this great 

 demonstration of the impossibility of the 

 spontaneous birth of germs in such culture 

 media, Pasteur himself in the subsequent 

 years of his life discovered the causative 

 germ of several important diseases. Similar 

 labours were also taken up by hundreds of 

 willing hands, and to-day the whole vast 

 science of bacteriology, with its immense 

 applications in modern medicine, surgery and 

 sanitation rests wholly upon this discovery, 



