CONTENTS. 



PAGE 



PREFACE TO THE ENGLISH EDITION v 



PREFACE ix 



INTRODUCTION ........ 1 



Importance of the study of immunity from a general point of view. Part 

 played by parasites in infective diseases. Intoxications by the products 

 of micro-organisms. Resistance of the organism to the invasion of micro- 

 organisms. 



Xatural immunity and acquired immunity. 



Immunity to micro-organisms and immunity to toxins. 



CHAPTER I 

 IMMUNITY IN UNICELLULAR ORGANISMS 11 



Infective diseases of the unicellular organisms. Intracellular digestion in 

 the Protozoa. Ainoebo-diastase. Part played by digestion in the 

 defence of the Protozoa against infective parasites. Defences of the 

 Paramaecia against micro-organisms. Part played by irritability in 

 defence in the lower organisms. 



Immunity of unicellular organisms to toxins. Acclimatisation of bacteria 

 to toxic substances. Protective secretion of membranes by bacteria. 



Adaptation of the Protozoa to saline solutions of yeasts to poisons of 

 yeasts to milk-sugar. 



Irritability of unicellular organisms and Weber- Fechner's psycho-physical law. 



CHAPTER II 



IMMUNITY IN MULTICELLULAR PLANTS 29 



Infective diseases of plants. Plasmodia of the Myxomycetes and their 

 chemiotaxis. Adaptation of the plasmodia to poisons. Pathogenic 

 action of Sclerotinia upon Phanerogams. The cicatrisation of plants. 

 Defence in plants against Bacteria. Sensitiveness of vegetable cells to 

 osmotic pressure. Adaptation of plants to modifications of osmotic 

 pressure. Dependence of the chemical phenomena upon the irritability 

 of the vegetable cells. The law of Weber-Fechner. 



CHAPTER III 



PRELIMINARY REMARKS ox IMMUNITY IN THE ANIMAL KINGDOM ... 40 



Examples of natural immunity among the Invertebrates. Immunity against 

 micro-organisms and insusceptibility to microbial poisons are two 

 distinct properties. The refractory organism does not eliminate micro- 

 organisms by the excretory channels^ It destroys them by a process of 



