XX11 



INTRODUCTION. 



which, however, are not so remarkable as those which are 

 induced by the chemical processes above alluded to. The 

 effects which may be trusted as being really due to electricity 

 should occur quickly after the passage of the current, and not 

 be limited to the part in the immediate neighbourhood of the 

 electrodes. If the current be allowed to pass for some time, 

 that is to say, for more than a few seconds, through the tissue, 



G 



the products of electrolysis first extend over the whole sur- 

 face lying between the electrodes, and then the intensity of the 

 current becomes extraordinarily reduced, frequently, indeed, to 

 zero, on account of the pole becoming covered with bubbles of 

 ;^as. On this account the employment of constant currents 

 for microscopic investigation is scarcely to be recommended, 

 for with the closure of even very weak currents, so violent a 



