PREFACE TO THE FIRST EDITION XV11 



whether the structure itself is perfectly sound. He 

 then builds further, but in most cases makes only a 

 tiny addition. It is very easy for a single observer 

 to lose a clear view of the whole, through using too 

 complicated a scaffolding. Others follow ; they test 

 the solidity of the structure, they move the misplaced 

 bricks into their correct position, and give a finishing 

 touch to the parts that are insufficiently trimmed. 

 Each new workman brings new tools, new ideas, and 

 his own extensive experience with him, and tackles 

 the whole structure from different points of view. 

 Then the scaffolding is removed, and a mighty build- 

 ing appears, which scarcely gives any idea how 

 diverse were the plans on which it was founded. So, 

 too, this contribution to our knowledge of the 

 functions of the cells may be considered only as an 

 attempt to adjust a new stone in the already existing 

 structure, and to construct a scaffold from which 

 further progress may be made. 



In conclusion, may I be permitted to express my 

 heartiest thanks to my collaborators, whose untiring 

 energy has made it possible to accomplish so many 

 single experiments in such a relatively short time, 

 and to work out different problems from various 

 standpoints at the same time. 



EMIL ABDERHALDEN. 



Halle a/S., 



April 15, 1912. 



