TO 



CARL LUDW1G 



PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OF I.EIPSIC 



AND 



L. RANVIER 



PROFESSOR OF HISTOLOGY IN THE COLLEGE DE FRANCE, PARIS 



TO WHOM THE AUTHOR IS INDEBTED FOR HIS EARLIEST TRAINING IN THE TRUE 

 METHOD OF MAKING AND RECORDING ORIGINAL OBSERVATIONS IN PHYSIOLOGY AND 

 HISTOLOGY, HE, WITH HEARTFELT PLEASURE, DEDICATES THIS WORK. 



IN OFFERING TO THEM THIS TRIBUTE OF HIS ADMIRATION AND REGARD, THE 

 AUTHOR DESIRES TO EXPRESS HIS SENSE OF THE INESTIMABLE ADVANTAGE WHICH 

 THEY HAVE CONFERRED ON PHYSIOLOGY AND HISTOLOGY. 



THEIR LABOURS, CHARACTERISED AS THEY HAVE BEEN BY ENTHUSIASM AND SINGLE- 

 MINDED DEVOTION TO THE ADVANCEMENT OF SCIENCE, HAVE NOT ONLY ADDKI; 

 GREATLY TO OUR FUND OF KNOWLEDGE, BUT HAVE ALSO DEMONSTRATED THE 

 SUPERIORITY OF THAT METHOD OF SCIENTIFIC OBSERVATION WHICH CONSISTS IN A 

 PATIENT AND INTELLIGENT SCRUTINY OF NATURE. 



TO THIS METHOD THEY HAVE ATTRACTED MANY DISCIPLES WHO ACKNOWLEDGE 

 THE INCALCULABLE VALUE OF THEIR PERSONAL INFLUENCE, THE CORDIALITY WITH 

 WHICH THEY HAVE ENCOURAGED AND DIRECTED THEM IN THEIR PURSUIT OF 

 ORIGINAL INVESTIGATIONS, AND THE GENEROSITY WITH WHICH THEY HAVE LAID 

 OPEN TO THEM THE RICH STORES OF KNOWLEDGE ACCUMULATED DURING A LIFE-LONG 

 STUDY OF THE PROBLEMS OF ANIMAL STRUCTURE AND FUNCTION. 



