420 BACTERIA IN INFECTIOUS DISEASES. 



tion by sick persons. A statement of the evidence 

 which has led the writer to this conclusion would 

 be out of place in the present volume, and with- 

 out further remark we must proceed to consider 

 the experimental evidence in favor of our a priori 

 reasoning. It must be admitted that this is very 

 unsatisfactory. 



The writer's personal investigations are recorded 

 in the " Preliminary Report of the Havana Yellow 

 Fever Commission of the National Board of Health/' 

 extracts from which report are given below. Un- 

 fortunately, the time allotted to this investigation 

 three months was entirely too short to make 

 a thorough experimental study ; and much of this 

 valuable time was necessarily consumed in perfect- 

 ing methods of research, and in gaining a knowl- 

 edge of micro-organisms encountered on every side 

 which were not yellow fever germs, but which could not 

 be excluded from consideration until this fact was 

 demonstrated. 



Evidently an extended acquaintance with the 

 bacterial organisms found during life and after 

 death in the bodies of persons not suffering from 

 yellow fever, and familiarity with the most ap- 

 proved methods of isolating and cultivating these 

 organisms, would have been of great advantage to 

 the investigator. But this preliminary knowledge 

 and special training was of the most imperfect 

 character. It was therefore evident that unusual 

 scientific caution would be required to compen- 

 sate, as far as possible, for a lack of previous special 



