1 6 THE STORY OF GERM LIFE. 



of impure cultures, that a student of to-day who 

 wishes to look up the previous discoveries in 

 almost any line of bacteriology need hardly go 

 back of 1880, since he can almost rest assured 

 that anything done earlier than that was more 

 likely to be erroneous than correct. 



The last fifteen years have, however, seen a 

 wonderful change. The difficulties had been 

 mostly those of methods of work, and with the 

 ninth decade of the century these methods were 

 simplified by Robert Koch. This simplification 

 of method for the first time placed this line of 

 investigation within the reach of scientists who 

 did not have the genius of Pasteur. It was now 

 possible to get pure cultures easily, and to obtain 

 with such pure cultures results which were uni- 

 form and simple. It was now possible to take 

 steps which had the stamp of accuracy upon 

 them, and which further experiment did not dis- 

 prove. From the time when these methods were 

 thus made manageable the study of bacteria in- 

 creased with a rapidity which has been fairly 

 startling, and the information which has accumu- 

 lated is almost formidable. The very rapidity 

 with which the investigations have progressed 

 has brought considerable confusion, from the fact 

 that the new discoveries have not had time to 

 be properly assimilated into knowledge. To- 

 day many facts are known whose significance is 

 still uncertain, and a clear logical discussion of 

 the facts of modern bacteriology is not possible. 

 But sufficient knowledge has been accumulated and 

 digested to show us at least the direction along 

 which bacteriological advance is tending, and it 

 is to the pointing out of these directions that the 

 following pages will be devoted. 



