24 MANUAL OF BACTERIOLOGY. 



To prove that boiling had not made the fluid unfit for the 

 growth of organisms, air was subsequently allowed to have 

 access to it without such precautions, when putrefaction 

 took place in the usual manner. 



At the same time it was demonstrated not only that bac- 

 teria are present in all fermenting and putrefying sub- 

 stances, but that they exist wherever there is animal life or 

 vegetation. 



These principles underlie the methods used daily for the 

 preservation of meat, fruit and vegetables, in the household 

 and in factories. 



Although even boiling occasionally failed to prevent fer- 

 mentation, investigators came with practice to have a 

 smaller number of failures. Such failures it was shown 

 were due to the presence of the resistant state called spores, 

 which some bacteria assume. The true nature of spores 

 was recognized later by Colin. Pasteur found that exposure 

 to temperatures above the boiling point (noC.) would 

 destroy the most resistant microbes and their spores. 



The controversies over fermentation and putrefaction 

 lasted almost until the present day. They were productive 

 of numerous benefits to the arts and manufactures. But 

 what is of more importance to our subject, they led to a 

 vastly better understanding of all kinds of microorganisms. 

 The study of bacteria was now pursued with great vigor. 

 In the space of about twenty-five years, most of what we 

 know concerning the bacteria of disease has been learned. 

 The period of rapid progress is not yet completed. Nearly 

 every year yields some advance of great importance. 



The discussions concerning fermentation and putrefac- 

 tion, were still going on when Lister made his brilliant 

 deduction that suppuration and septic processes in wounds 

 were a species of fermentation (1867). From this came the 

 antiseptic and aseptic methods of operating and of dressing 



