INTRODUCTION. 



The following pages are an abstract of a short 

 series of lectures delivered by request to the 

 class of 1905 in the Harvard Medical School, 

 in January, 1903. The method of illustrating 

 Ehrlich's theories is given in an attempt to 

 make this obscure subject somewhat more clear, 

 and the glossary of terms, may prove useful to 

 beginners. 



