Fluctuating or Alternating Hydration Effects. 



89 



one of the old ones. The swelling during the next two and a half hours 

 was equivalent to 500 per cent on the basis of the average thickness 

 of the four sections in action. 



A second fresh section was placed imder another old one, making 

 five sections in action. The swelling during the next 3 hours was 

 something over 300 per cent, calculated on the basis of the five sections 

 engaged. The third fresh section was now added, giving a preparation 

 in which sections were included in four different stages of swelling, with 

 an initial average thickness of 0.36 mm. The swelling during the next 

 three and a half hours was about 225 per cent of the initial thickness 

 and reached an end-point 20 hours after the experiment was begun 

 at 1,333 per cent of the total, which was in excess of that reached in the 

 previous test. The temperature underwent a range of from 15° to 

 22° C. (fig. 16). 



Fig. 15. — Courees of swelling of sections of agar and peptone, a fourth, fifth, and sixth fresh (dry) 



section being added as indicated. 



The water was now removed from the dishes and the double trio of 

 sections was subjected to the action of a 2 M solution of calcium 

 chloride. A shrinkage followed which terminated with some abrupt- 

 ness at the end of an hour and reduced the thickness of the swelled 

 sections 1.05 mm. or nearly 300 per cent of the original. Calculated 

 -on the basis of the swelled sections, which had reached a total average 



Ban 



T 



2arr 



Fio. 16. — Variations in volume of double trio of sections of agar and peptone which had reached 

 full hydration in distilled water and were then immersed in calcium chloride, 2M. 



thickness of 4.8 mm., the reduction was nearly 22 per cent. A swell- 

 ing now followed and practically half of the thickness lost was regained. 

 Most of this was completed within 2 hours, after which a very slow 

 rate of increase followed, which was not at an end at the close of the 

 third day. This test also was carried on at room temperature, which 

 underwent a wide variation, as noted above (fig. 16). 



