. RELATION OF ENDOSMOSIS TO CAPILLARY ATTRACTION. 57 



water impregnated with carbonic acid : in a very short time, the acid gas, leaving the 

 water, went through the barrier, and as it accumulated in the jar, was delivered by the 

 short tube at the other end, and passed up in bubbles through the water. 



178. Branchial respiration deviates still more from the simple type, for we have here 

 two fluids, presenting gaseous matter to each other for interchange through a membra- 

 nous screen. In one of them the gas is in a state of solution only, but as to what its 

 condition in the other may be, we can scarcely say. The phenomenon, however, becomes 

 obviously much more complex. In bronchial respiration, the account which Mr. Graham 

 gives of the process by which the little cells empty themselves into the trachea is prob- 

 ably correct ; and the same observation undoubtedly applies to the case of the respiration 

 of insects. 



179. The issue of these investigations, besides co-ordinating the observations of Dr. 

 Mitchell and Professor Graham, has a far more important application. It shows us 

 indisputably that membranes have special mechanical functions depending on the condi- 

 tions of their texture; and that often they are, in appearance, the .generators of power 

 equal to the pressure of many atmospheres. It is not pretended, however, that the 

 foregoing paragraphs contain the whole theory of cellular action, the object of this 

 communication being limited to a discussion of some of those mechanical functions 

 which have led chemists to conflicting results. Writers on physiology have suspected 

 that membranes were springs of power, both mechanical and chemical, but the direct 

 proof, from actual experiment, has never until now been furnished. 



CHAPTER VII. 



THE PHYSICAL THEORY OP ENDOSMOSIS. 



(From the American Journal of the Medical Sciences for August, 1838.) 



CONTENTS : Relation of Endosmosis to Capillary Attraction. Cases of reported Decom- 

 positions. Can be produced by Inorganic Masses, and therefore not due to Vitality. 

 Water made to wet -Mercury. Voltaic Battery controls Capillary Attraction. Ac- 

 tion of Inorganic Tissues. Water passes through excessively small Pores. Hy- 

 draulic Currents. Deposites produced by Endosmotic Currents. Apparent Decompo- 

 sition of Metallic Salts by Membranes. True Theory of it. General Conclusion that 

 Endosmosis is nothing more than common Capillary Attraction, and never occasions 

 true Decompositions. 



180. IT is the object of this communication to offer some proofs that the peculiar 

 force known to chemists and physiologists under the title of endosmose and exosmose, 

 has no existence independently of ordinary capillary attraction ; and that all the cases 

 described as chemical decompositions, brought about by the intervention of animal 

 membranes and areolar tissues, are only examples of the play of ordinary and well- 



known agents. 



H 



