PREFACE. XV11 



must in the present day possess this character. 

 From a certain number of observations it must 

 enable us to draw some conclusion, whether it be 

 extended or limited. 



The imperfection of the method or system of 

 research adopted by physiologists can alone explain 

 the fact, that for the last fifty years they have esta- 

 blished so few new and solid truths in regard to a 

 more profound knowledge of the functions of the 

 most important organs, of the spleen, of the liver, 

 and of the numerous glands of the body ; and the 

 limited acquaintance of physiologists with the me- 

 thods of research employed in chemistry will con- 

 tinue to be the chief impediment to the progress of 

 physiology, as well as a reproach which that science 

 cannot escape. 



Before the time of Lavoisier, Scheele, and 

 Priestley, chemistry was not more closely related 

 to physics than she is now to physiology. At the 

 present day chemistry is so fused, as it were, into 

 physics, that it would be a difficult matter to draw 

 the line between them distinctly. The connection 

 between chemistry and physiology is the same, and 

 in another half-century it will be found impossible 

 to separate them. 



Our questions and our experiments intersect in 

 numberless curved lines the straight line that leads 

 I 



