INTRODUCTION xvii 



inhibition by fresh plasma of the actual growth of bacteria. Fliigge 

 and Nuttall in 1888 demonstrated under the microscope the destruc- 

 tion of bacteria by blood, and Buchner in 1889 showed this property 

 to be present in the serum. At about the same time the work of 

 Richet and Hericourt and of Babes and Lepp showed that an 

 immunity artificially produced against pyogenic cocci and against 

 the virus of rabies could be transferred from one animal to another 

 by means of the blood serum. These studies were followed almost 

 immediately by the discoveries of Behring and Kitasato that the 

 serum of animals immunized to the toxins of tetanus and of diph- 

 theria bacilli not only could produce immunity in other animals, but 

 that the specific disease could be cured by the use of the respective 

 sera. These discoveries led immediately to the development of serum 

 therapy, and in 1894 diphtheria antitoxin was being marketed in 

 Germany. Contemporaneously with these developments Metchnikoff 

 conducted his observations and experiments upon phagocytosis, and 

 in 1883 published his " Recherches sur la digestion intracellulaire." 

 He studied various lower forms of life, such as echinoderms, and 

 found that during metamorphosis the atrophic cells of the larvae are 

 devoured by other cells, either leucocytes or other phagocytic cells. 

 These studies were later extended to include reparative conditions, 

 such as the healing of wounds and resistance to infection. The out- 

 come was a series of brilliant discoveries of the part phagocytosis 

 plays in combating bacterial invasion, and ultimately the practical 

 application in the use of bacterial vaccines for prevention and treat- 

 ment of infectious disease. The discovery of the various forms of 

 immune bodies and of the substances which might lead to the pro- 

 duction of such immune bodies followed with considerable rapidity, 

 but the details may best be left to the study of the particular immune 

 bodies concerned, which include agglutinins and precipitins, cytoly- 

 sins, and other complement binding substances. " That a plague 

 of diarrhea in a poultry yard, studied by a professor of chemistry, 

 should be the seed from which has grown the vast development of 

 later years is a strange fact, but fact, nevertheless " (Adami). 



