( 378 ) 



It will be seen that the longer the epithelium is left in contact 

 with the salt-solution, the less is the difference in volume. In this 

 case a contact even of two hours is not sufficient to effect a complete 

 exchange between the contents of the cell and its surroundings. At 

 the end of the experiment, we can, by putting a preparation in a 

 gas-camera and passing CO2 through it, still set the cilia in movement. 



Experiment XXIII. 



From this experiment we learn that, after half an hour's immer- 

 sion, the volumina still differ, but after two hours only very little, 

 and as little after three. After two hours thus the exchange 

 between the contents of the cell and its surroundings is almost 

 completely accomplished here. 



At the end of the experiment the epithelium was still alive. 



From these experiments^ then, we may conclude that the cilianj- 

 epithelium in a live state allows Na Cl-solutions to pass through it, 

 though not so rapidly as does the intestinal epithelium. 



This permeability of the isolated epithelium, which, although con- 

 siderable, will of course be more intense in situ, is quite in accor- 

 dance with the clinical experience, that remedies injected intratra- 

 cheally are very rapidly resorbed. About the permeability of the 

 nucleus, can be said the same what has been observed with respect 

 to the intestinal epithelium. 



III. BLADDER-EPITHELIUM. 



If with the intestinal- and tracheal-epithelium we had to do with 

 cells which might be expected to be easily permeable to salts, the 

 reverse was to be expected of bladder-epithelium. The bladder, 

 indeed, would very badly answer its purpose, if it possessed a great 

 permeability for dissolved substances. 



