Fluctuating or Alternating Hydration Effects. 83 



ness. Replacement with acid (F) resulted in a further slight shrink- 

 age, no noticeable loss ensuing when the acid was replaced by acidified 

 salt (Or) . Replacement with alkaline salt (H) was followed by an in- 

 crease which had ceased at the end of 4 hours. Water now caused a 

 slow continued swelling (/), at which time the maximum size of the 

 sections was reached and they had swelled 2,400 to 2,800 per cent of 

 the diameter of the dried plate. 



Replacement of the water by an acidified solution (/) resulted in a 

 very rapid shrinkage, which was nearly complete in an hour and re- 

 duced the sections nearly 200 per cent of the original. Replacement 

 of the acidified salt by water (K), which was renewed three times, 

 regained only about half of the thickness lost in the acidified salt. It 

 is to be remembered that the sections were in a condition of acidosis, 

 and this would not be reduced below a certain point until alkali was 

 introduced. This was done in an alkaline salt (L), which produced a 

 very slight shrinkage. The swelling in water following this treatment 

 was of such reduced amplitude that the measurements were discon- 

 tinued. The successive treatments had resulted in the incorporation 

 of water to the full imbibition capacity of the colloid, and the reagents 

 had produced such changes that mere variations in acidity, alkalinity, 

 etc., caused but little variation in this amount and in the volume of 

 the sections, a condition in general analogous to that of a mature organ. 



A series of tests were now planned to induce alterations in sections 

 in which imbibition was first carried to a degree near the saturation- 

 point. Sections of agar 90 parts, bean protein 10 parts, 0.16 mm. in 

 thickness, swelled 2,156 per cent in 18.5 hours at 16 to 18 C., and 

 the rate of expansion had fallen very low. Substitution of a hun- 

 dredth-normal potassium-nitrate solution checked further increase and 

 induced a very slight shrinkage in 6.5 hours, and no perceptible alter- 

 ation took place by the substitution of citric acid (0.01 M) for 15.5 

 hours. Replacement with potassium hydroxid + potassium nitrate 

 (0.01 M) resulted in a swelling of 156 per cent of the original dimen- 

 sions in 8 hours, at the end of which time this action had entirely 

 terminated. The sections now being in an alkaline condition, their 

 immersion hi water was followed by an increase of 1,250 per cent of 

 the original dimensions, the total now being 3,406 per cent. 



Replacement of the water by a hundredth-normal solution of potas- 

 sium nitrate and citric acid resulted in a greater change than at a 

 lower water-content, the shrinkage now being 190 per cent of the origi- 

 nal diameter of the air-dry plate. When the sections had swelled but 

 2,156 per cent, the action of a similar solution did but little more than 

 check swelling. 



The biocolloid at this last point was equivalent to a protoplasm in 

 its water-relations which contained over 95 per cent water and less 

 than 5 per cent dry matter. In a later stage the biocolloid was made 



