many, opsonins and vaccine therapy, have gone into disrepute as did tuber- 

 culin nearly twenty years ago. We now know tuberculin has many appli- 

 cations of importance in the diagnosis and treatment of tuberculosis, though 

 this knowledge has been gained some years later than it would have been had 

 it not been for improper exploitation. In the hope of avoiding a repetition 

 of such an effect as far as opsonin and bacterial vaccines are concerned, this 

 subject is given considerable attention. The opsonic index technique which 

 is given here is the one taught the writer by Dr. W. G. Ross, who was for two 

 years a pupil of Sir A. E. Wright. 



An attempt has been made to bring the subjects taken up as nearly up 

 to date as is possible. It is hoped that this work may furnish to the medical 

 student and practitioner information which may lead him to a better under- 

 standing of the nature of infections and the subjects of immunity, and active 

 and passive immunization. 



Columbia, Missouri, April, 1909. 



