346 PROCEEDINGS OF THE AMERICAN ACADEMY 



separated by a porous partition or by a membrane, that a serious error 

 might arise in using even the pads or cushions of Du Bois Reymond, 

 arising from the action of the vital fluids of the muscle upon the sul- 

 phate of zinc through the clay or membranous guards. 



In experimenting upon the action through membranes I used an ob- 

 long vessel divided into four partitions by means of pieces of pig's 

 bladder soaked in the white of an egg. In the outer compartments 

 were placed the zinc electrodes in the solution of sulphate of zinc, and 

 in the middle compartments the liquids to be examined. Owing to the 

 unequal action of the sulphate of zinc through the partitions, even 

 when the inner compartments were filled with one and the same liquid, 

 an energetic swing of the needle of the galvanometer resulted. 



The experiments with this apparatus made it evident that a very 

 slight difference in the partitions enclosing a fluid and separating it 

 from a surrounding homogeneous connecting liquid, together with the re- 

 sulting endosmotic action, is sufficient to produce an electrical current. 



I next made use of the apparatus of Du Bois Reymond, which I have 

 already described. Having connected the two cushions by the con- 

 necting pad, and having laid a piece of bladder treated with the white 

 of an eg"r over the connection thus formed, I made use of a series of 

 tubes filled with the following liquids : 



Distilled water. 



Undistilled water. 



Blood. 



Solution of salt. 



Solutions of iron. 



Applying these tubes, having covered their openings with bladder, 

 upon the connecting guard, I found that each liquid gave rise to a 

 current which varied in direction with the nature of the fluid. These 

 currents were evidently due to the action of the fluid in the artificial 

 muscles upon the sulphate of zinc in the connecting guard, for distilled 

 water gave no appreciable current, and the mere contact of the bladder 

 of the tube upon the bladder of the guard was insufficient to produce 

 an action. In order to be certain of this, I next made use of a vessel 

 shaped like a U tube, with an opening at the bend, and having covered 

 the ends of the tube with a membrane, I injected into the two limbs 

 the liquids with which I experimented. When the vessel was 

 filled with a homogeneous fluid, a deflection of the needle of the gal- 

 vanometer was produced. Upon the reversal of the points of contact 



