58 



CARNEGIE INSTITUTION OF WASHINGTON. 



surface of the cellulose fibers of the wall. After remaining in the alcohol 

 15 minutes the preparation was removed and dried in the air-current from an 

 electric fan, which required about 3 hours. 



The thimbles were now filled with a 3 per cent solution of lecithin in water 

 and allowed to stand 10 minutes. The lipin would be carried into the inter- 

 stices in the fiber and between the granules and locked there by the beginning 

 hydration of the agar particles and of the fibers of cellulose. The lecithin 

 was now drained out and the cell was ready for being fitted with whatever 

 plasmatic lining was desired. If agar alone was used, a few cubic centimeters 

 of a liquid solution was run in through the filling-tube at about 60° C. and the 

 cell revolved slowly in the hand to allow it to set as a uniform layer. The 

 resulting total arrangement was one which colloidally represented the arrange- 

 ment of the living cell with such fidelity as to furnish some very important 

 information. 



Such a cell showed a much higher rate of activity with relation to its vacu- 

 olar contents than the earlier cell with a clay waU. As constructed, the new 

 type had a capacity of 15 to 20 c. c, or about haK that of the original cell. 

 The earlier type of cell with the clay walls did not reach its maximum activity 

 with whatever contents until the second, third, or fourth day at 15° C. The 

 improved cell became fully functional (compared with the living cell) much 

 earlier and at a time determined by the nature of the contents. This was 

 taken to be due entirely to the character of the outer wall. 



The outer wall of the new cell was made up of aggregated agar particles 

 infiltrated with lecithin. When placed in water, both the lecithin and the 

 agar hydrate very slowly, and the agar at room temperatures does not liquefy. 

 It follows, therefore, that when cells were filled with sugar solutions, for example, 

 this hydration would proceed very slowly. So long as the particles retained 

 full individuality the layer which they form would be highly permeable. 

 Sugar-filled cells (10 per cent), therefore, showed but little activity on the 

 first day, but the swelling of the agar proceeded at such rate that on the 

 second and third days a layer or membrane of some density would be com- 

 pleted and then water would pass more rapidly than sugar with a resultant 

 endosmose. Increase in the volume of the contents was followed, of course, 

 by an outflow through the delivery-tube which was measured directly. 



The chief value of such a cell is that its action shows the effects of the salts 

 which are being absorbed on the colloidal material of the walls and mem- 

 branes of cells. This may be illustrated by the following results of the action 

 of cells with various contents when immersed in water: 



