PREFACE. XXxiil 



they were the pillars and air passages which 

 protected the mine from water and from foul air. 



Every chemical or physical investigation, 

 however insignificant, which lays claim to at- 

 tention, must in the present day possess this 

 character. From a certain number of obser- 

 vations it must enable us to draw some conclu- 

 sion, 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 established 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 acquaint- 

 ance of physiologists with the methods of re- 

 search employed in chemistry will continue 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 re- 

 lated 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 diffi- 

 cult matter to draw the line between them 

 distinctly. The connexion between chemistry 

 and physiology is the same, and in another half 



