44 Hydration and Growth. 



colloid below that in the salt alone. A wide variety of tests which gave 

 opportunity for comparisons are described throughout this volume, 

 but a few may be recorded here which were carried out expressly to 

 obtain evidence on this point with biocoUoids of different constitution. 

 Nucleinic acid is a constituent of the nucleus, and as the only other 

 substance from this body which had been introduced into the tests 

 which could be assigned to the nucleus was peptone, its swelling re- 

 actions were tested with much interest. The results of swellings of 

 these substances, when combined in proportion of 10 parts nucleinic 

 acid to 90 parts agar, are given in table 30. 



Table 30. 



p. ct. p. ct. 



DistUled water 1,400 1,025 



Potassium nitrate, 0.01 M 900 800 



Potassium nitrate, citric acid, 0.01 N 650 675 



Potassimn citrate, 0.01 N 850 760 



Potassiimi citrate, citric acid, 0.01 N 725 



Citric acid. 0.01 N 700 625 



Sodium hydroxid, 0.01 M 1,000 925 



A second series a week later gave measurements shown in table 31. 



Table 31. 



p. ct. p. ct. 



Distilled water 950 1,100 



Potassium nitrate, 0.01 M 650 650 



Potassitun nitrate, citric acid, 0.01 N 675 600 



Citric acid, 0.01 N 575 450 



Potassium nitrate, potassium hydroxid, 0.01 N 900 760 



Potassium hydroxid, 0.01 M 850 800 



This mixture is seen to swell most in distilled water, while the pro- 

 portionate swelling in hydroxid is very high, being greater than that in 

 the salts tested or in acid. Next, it is apparent that the two potassium 

 salts produce or allow an amount of imbibition not very much short 

 of that in the hydroxid. The acidification of the salts practically 

 reduces the swelling to the proportion displayed by the acid alone. 

 This must be taken to apply to this set of combinations only. It may 

 not be assumed that a similar generalization would hold for calcium. 



Following the above, plates composed of 90 parts agar and 10 parts 

 glycocoU, 0.15 mm. in thickness, were tested in series parallel to the above 

 in the dark chamber at 16° C. The swellings are given in table 32. 



Table 32. 



p. cL p. ct. 



DistiUed water 1,300 1,266 



Potassium nitrate. 0.01 M 700 1,000 



Potassium nitrate, nitric acid, 0.01 N 900 766 



Citric acid, 0.01 N 666 766 



Sodium hydroxid. 0.01 M 366 300 



The effects of the acidified salt and of the acid are of the kind pre- 

 viously noted. The most prominent feature of the reactions was the 

 low hydration capacity in the alkaUne solution and the relatively high 



