PREFACE vii 



lowed the example of Bordet. We tried to show that the 

 phenomena observed might be explained on the supposition 

 that diphtheria toxin is a simple substance which slowly 

 decomposes into an innocuous material that still neutralises 

 antitoxin. In his explanation Ehrlich had previously 

 assumed the presence in the diphtheria poison of a large 

 number of poisonous substances of different strength. 

 Now Ehrlich did not wish to yield this explanation, which 

 he regards as the principal point in his doctrine; and 

 therefore he and his numerous pupils raised a number of 

 objections to the treatment of this branch of science in 

 accordance with the modern theories of chemistry. There- 

 upon Biltz, encouraged by Ehrlich, took up and elaborated 

 the old idea of Bordet, which had been abandoned by this 

 prominent savant in favour of the chemical hypothesis, 

 and suggested that antitoxin does not react chemically 

 with toxin, but behaves about in the same manner as a 

 dye when it becomes fixed in a fibre. 



Some of these recent objections to the ideas brought 

 forward in the lectures have been taken here into consid- 

 eration, notwithstanding that they have appeared since the 

 lectures were delivered. In the same way, much recent 

 work, especially by Madsen and his pupils (in large part 

 as yet unpublished), bearing upon the velocity of reactions, 

 has been given consideration in the following pages. And 

 the recent work of Hamburger on precipitins has been 

 made use of in the final chapter. 



I have given to these lectures the title " Immuno-chem- 

 istry," and wish with this word to indicate that the chemical 

 reactions of the substances that are produced by the injec- 

 tion of foreign substances into the blood of animals, i.e. by 

 immunisation, are under discussion in these pages. From 

 this it follows also that the substances with which these 



