LOUIS PASTEUR. 237 



facture, and at the same time enabled Pasteur to demonstrate 

 that his theory of fermentation, and not that of Liebig, was 

 undoubtedly the correct one. 



To-day it seems almost impossible that only so recently 

 as a little over twenty years ago, the theory of spontaneous 

 generation should have been thoroughly believed in, and 

 that ingenious experiments were made and great ability dis- 

 played in defence of this theory as regards the development 

 of living bacteria. Van Helmont's evolution of mice from 

 a pot charged with corn and stuffed with a dirty shirt, and 

 his statement that the smells which arise from the bottom 

 of morasses produce frogs, slugs, leeches, grasses, and other 

 things, are now looked upon as scarcely more extraordinary, 

 although they date back a couple of hundred years. 



Having studied the process of fermentation and noted 

 the relation of effect to cause, and having also noticed that 

 the commencement of fermentation and putrefaction pro- 

 cesses were invariably associated with the process of seeding 

 out, through the deposition of living organic particles in his 

 nutrient media, he naturally — I say naturally because Pasteur 

 was the observer and logician who was investigating the 

 point under consideration — came to the conclusion that 

 living organisms like all animal and vegetable cells were 

 developed only by a process of reproduction or division 

 of the parent organisms. So many difficulties did the 

 problem " Abiogenesis " appear to present, that when 

 Pasteur informed M. Biot that he intended to study this 

 question, the latter assured him "you will never escape from 

 it. you will only lose your time," whilst his teacher and 

 friend, M. Dumas, said that he would not advise any one to 

 occupy himself too long with such a subject. Pasteur re- 

 peated Schwann's experiments of boiling organic fluids and 

 then allowing only air which had been passed over red-hot 

 platinum, to come in contact with these fluids, with the result 

 that no evidence of organic life made its appearance even 

 in those which were most decomposable, such as urine. He 

 also showed that on boiling the putrescible fluid in a flask 

 with a long narrow sinuous neck left unclosed, the fluid 

 will remain perfectly clear, and no growth will take place, 



