PREFACE. V 



shelter behiud Lavoisier's well-known and convenient apology: "Man would never 

 give anything to the public if he waited till he had reached the goal of his under- 

 taking, which is ever appearing close at hand and yet ever slipping farther and 

 farther as he draws nearer." Those who dwell in the clearer light of the next 

 generation will build better than we have done and will scarcely realize how slowly 

 and painfully many of us have groped about for what seems to them so plain. 



In conclusion, I desire to make grateful mention of Dr. Theobald Smith, 

 professor of comparative pathology in Harvard University Medical School, and Dr. 

 Veranus A. Moore, professor of comparative pathology and bacteriology in Cornell 

 University, each in turn in charge of the animal pathological investigations of the 

 Bureau of Animal Industry, United States Department of Agriculture, at a time 

 when the writer was beginning his bacteriological studies and was perplexed in 

 many ways. To friendly advice and helpful suggestions from these distinguished 

 men he owes more than he can well repay. 



AUGUST 25, 1905. 



