PREFACE 



THE enormous progress of medical science during the last twenty- 

 five years has in great part been the outcome of the experimental inves- 

 tigation of the interrelation between the macro- and microorganism 

 during infection. The study of this subject, while still in its infancy, 

 has already yielded results of such extreme practical value, and so 

 far-reaching in their biological significance that the time has come 

 when the general practitioner who would understandingly follow that 

 portion of the current medical literature which may be said to repre- 

 sent the truly romantic side of modern medicine should familiarize 

 himself with the essential basis upon which the new science of 

 immunology has been established. The present work has been 

 written with this end in view. It is intended, as the title indicates, 

 as an introduction to the study of infection and immunity and of 

 the application of immunological principles to diagnosis and treat- 

 ment. To those who are interested the author would suggest to 

 start at the beginning and to read the first eleven chapters in 

 succession. A picture is here developed of the conflict which takes 

 place when the opposing forces of the invading and the invaded 

 organisms are brought together. Each chapter in question repre- 

 sents the basis for the one succeeding. The final chapters may 

 then be read at random. 



The development of any new branch of science necessarily brings 

 with it a new terminology, and this factor no doubt has been largely 

 responsible for the hesitancy with which the general practitioner 

 has in the past approached the study of questions of this nature. 

 The author has attempted not to overburden the text with new 

 terms, and to introduce those which are actually necessary, in a 

 gradual manner, so that the physician may acquire an immunological 

 vocabulary as he proceeds with his reading. 



In the second part of the work, in which the practical application 

 of immunological studies to treatment and diagnosis are taken up, 



