x PREFACE 



lated, but no attempt has been made to record 

 herein all the literature references on the sub- 

 ject; only a few of the more recent and impor- 

 tant references being cited. 



We are indebted to Dr. William H. Park, Di- 

 rector of the Bureau of Laboratories of the New 

 York City Department of Health, for the privi- 

 lege of using his copyrighted illustrations of 

 bacteria. Some of the photographs of the pio- 

 neers in immunology are from portraits in Li- 

 brary Hall of the Army Medical Museum at 

 Washington, D. C. 



MEDICAL DEPARTMENT 

 LEDERLE ANTITOXIN LABORATORIES 

 New York 

 May, 1915 



