INTRODUCTION 



THE last quarter of a century has witnessed an almost marvelous 

 development of knowledge in the domain of medicine and the allied 

 sciences, only a part, of course, of the extensive progress made in the field 

 of general science. A striking portion of this advance has tended to 

 broaden our knowledge of the principles and of the essential details of 

 the processes of infection and immunity, until these branches have today 

 come to form almost a special science in themselves an. imperium in 

 imperio. Aside from the personal factor, the writer's immediate inter- 

 est in the present volume, as originally projected, arose from the fact 

 that he was desirous of having appear a series of exercises illustrative of 

 the principles of immunology a class-book intended to set forth in 

 permanent form the very excellent course of instruction that Dr. Kolmer 

 has been giving during the past few years to selected groups of in- 

 terested students and occasional post-graduate workers in the Medical 

 School of the University of Pennsylvania. That it should have sur- 

 passed the original simple plan and grown into a volume of the present 

 proportions is scarcely to be wondered at, if the temptation to elaborate 

 the individual exercises by explanations and cognate considerations was 

 in the slightest to be yielded to. This is due to the fact that in its 

 growth the subject has acquired so much of undoubted importance in 

 the form of isolated observed facts, and itself presents so many analogies 

 and has led to so extensive a terminology, that the author who would 

 attempt to link the observed facts into anything like logical sequence 

 or to add in the least to the bare cook-book-like series of illustrative 

 exercises any explanatory paragraphs, cannot avoid the fullness that 

 Dr. Kolmer has found inevitable in presenting the subject. 



The branch of immunology, including primarily infection, and its 

 ramifications into diagnosis and the actual treatment of disease, has 

 brought to the parent subject of preventive medicine the greatest offer- 

 ing of the decades of its growth. Itself contributing to world expansion, 

 it has nowhere found a greater stimulusthan in the field of exotic pathol- 

 ogy; and this last, in turn, has enriched internal medicine, even in its 

 most common aspects. The first step in immunology may properly be 

 ascribed to Jenner, with his bovine vaccine for smallpox, a step followed 



