TEANSLATOR'S PEEFACE 



In bringing an English translation of this work before the 

 public, I feel that a word or two of explanation is due to 

 my readers. Many people regard the translation of French 

 or German scientific works as unnecessary, holding that 

 every student of science should have a knowledge of these 

 languages-. Without wishing to controvert this opinion 

 generally, I may state the reasons which originally prompted 

 me to undertake this translation. In the first place, 

 the investigations here described are of so fundamental a 

 nature as to be of interest not only to workers in all the 

 various branches of Biology, and to physicists, but perhaps 

 even to those who are not professed students of science at 

 all. In the second place, this work, lying as it does for the 

 most part on the border-line between two sciences so 

 distinct as Physics and Biology, is full of the technicalities 

 of both these sciences, and is therefore by no means easy 

 reading in the original for a modern scientific specialist, 

 however great his knowledge of the German language. 

 Por these reasons it seemed to me that a translation of 

 Professor Biitschli's valuable investigations might form an 

 acceptable addition to English scientific literature. 



In preparing this translation certain German words 

 and phrases were found especially difficult to render into 

 English. Above all, this was the case with the two words 



