EDITOR'S PREFACE. 



IN the Editor's Preface to Baron Liebig's " Researches on the Chemistry 

 of Food," in which the Author gave the results of his investigation into the 

 constituents of the juice of the flesh, I mentioned that Baron Liebig had 

 been led to study the subject of Endosmosis experimentally. The results 

 of this investigation are contained in the following pages ; and the reader 

 will, I trust, be satisfied that the motions of the animal juices depend on 

 something more than mere Endosmosis or Exosmosis, and that the pressure 

 of the atmosphere, as well as its hygrometric state, by influencing the 

 transpiration from the skin and lungs, are essentially concerned in pro- 

 ducing these motions. At the same time, the present work is to be regarded, 

 not as exhausting the subject, but, on the contrary, as only pointing out 

 the direction in which inquiry is likely to lead to the most valuable 

 results. 



While it is proved that the mechanical causes of pressure and evapora- 

 tion, and the chemical composition of the fluids and membranes, have a 

 more direct, constant, and essential influence on the motion of the animal 

 fluids, and, consequently, on the state of the health, than has been usually 

 supposed, it is evident that very much remains to be done in tracing that 

 influence under the ever varying circumstances of the animal body, and 

 in applying the knowledge thus acquired to the purposes of hygiene 

 and therapeutics. But it is equally obvious, that the above-mentioned 

 mechanical and chemical causes are not alone sufficient to explain the 

 phenomena of animal life, since they are present equally in a dead and in a 

 living body ; so that while every advance in physiology enables us to explain 

 more facts on chemical and mechanical principles, something always 



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