Mitchell on the Penetrativeness of Fluids. 317 



infiltrator and diluent, a knowledge of whose habitudes will be thus 

 rendered both clearer and more useful. 



Before closing my remarks, I am happy to be enabled to say, that 

 a considerable number of my medical friends visited my laboratory, 

 and saw for themselves the verifications of my statements. I 

 solicited their observation, both for the confirmation of my own 

 impressions, and for the greater readiness of reception which the 

 public always affords to facts which have appeared in a similar 

 light to several different individuals of adequate judgment. 



In my next I hope to present a table of the rates of penetrative- 

 ness of liquids for animal membranes. I hope also to ascertain the 

 amount of force. On the relation of the respirable gases to the 

 blood, and other liquids, I possess already many interesting facts, 

 which will be then promulged. 



Philadelphia, September 152A, 1830. 



Since the foregoing paper was sent to the editor of this Journal, 

 I have had an opportunity of reading M. Dutrochet's short essay, 

 entitled * Nouvelles Recherches, &c.' In it I find that the author 

 has discovered his mistake relative to the action of acids in general, 

 but has fallen into one quite as important, respecting the agency of 

 diluted sulphuric acid. He now considers it a nullifier of endos- 

 mose, instead of a promoter of exosmose, being not only itself inac- 

 tive, but the cause of inactivity in other solutions. Feeling confident 

 of the power of diluted sulphuric acid to receive as much water as 

 the animal membrane could convey, I, in conjunction with Professor 

 Finley, carefully repeated our experiments on that substance. In 

 every case, where the solution exceeded 1, (Beaume,) it was ade- 

 quate to the occupation of as much water as could be presented 

 by the membrane. At 2, 11, and 25, the acidulous liquid gave 

 the same rate of aqueous infiltration as did alcohol, ether, &c. A 

 solution of sulphate of soda, at 11, and at 3 Beaume', and a solu- 

 tion of ammonia at 40 centesimal alcometre, being infiltrable by 

 water, at a rate not less than that of the animal membrane, of course 

 afforded, w,hen compared with that liquid, exactly the same results. 

 Although all these substances gave evidence of having been con- 

 temporaneously transmitted through the membrane, yet the quantity, 

 easily appreciated chemically, was not so great as to make a sensible 

 difference in the altitude of the column, whose rise represented the 

 transmission of water. When, by the entrance of a considerable 

 quantity of water, the acid was so far diluted as to intermingle with 

 it more slowly than the membrane could present it, a rapid diminu- 



