Hydration and Growth of Colloids and Cell-masses. 



115 



tion, however, suggest that even in hydrating colloids, in which meta- 

 bolism is not in progress, abrupt modifications may occur by the con- 

 junction or disjujiction of two important reactions of the constellation 

 present. 



The chamber in which these tests were made was under ground, 

 with earthen and board walls, and was reached through an entrance 

 chamber. Electric heaters were used. The chamber was 2.7 by 2 

 by 2.2 meters and it was necessary to enter and work in it when making 

 the tests. The air was stirred by a fan and a mercurial thermometer 

 suspended from the ceiling showed air temperatures several degrees 

 above that of the water in the dishes. Thus, in the preceding test, 

 the observer was in a humid atmosphere at 55° C. (131° F.) when 

 the readings of the swellings were 48° to 49° C. 



The compilation of averages (table 94) affords a ready means of 

 comprehension of the essential features of the entire series. 



A series of swellings of agar sections 0.18 mm. in thickness, made 

 at the same time, affords valuable data for comparison with the in- 

 creases of the complex biocoUoids (table 95). 



The hydration reactions of the agar are not so positive and uniform 

 as those of the more complete systems. Increase by absorption had 

 not reached a positive final in 24 hours at the lowest temperature. A 

 similar stage of satisfaction was evident in half this time at about 

 40° C. and in 8 hours at 49° C. The rate of swelling is graphically 

 illustrated in figure 21. 



The maximum or "optimum" of swelling of such agar plates occurs 

 at some temperature near 40° C. Initial rate and total increase are 

 greatest at this point. The maximum swelling of the agar, bean pro- 



