32 Hydration and Growth. 



TABLE 12. 



p. ct. 



Water 1 ,400 



Potassium nitrate, 0.01 M 1 , 200 



Potassium nitrate, citric acid, 0.01 N 900 



Citric acid, 0.1 N 675 



Potassium nitrate, potassium hydroxid, 0.01 M 575 



Potassium hydroxid, 0.01 M 400 



The hydration in all the solutions was less than in the earlier tests, 

 partly due, no doubt, to the difference in the peptones used. The 

 increase in hydroxid is small; no direct comparison can be made as to 

 the acid, as a hundredth-normal solution was used in the other tests, 

 while the swelling in acidified salt solutions is relatively large. Such 

 results emphasize the fact that material standardized for cultural 

 and chemical purposes may present differences in colloidal action of a 

 serious character. 



Nucleinic acid is a substance of interest in connection with its 

 occurrence in the nucleus and its direct effect in simple combination 

 was tested. A mixture of 90 parts agar and 10 parts nucleinic acid 

 was dried into plates 0.2 mm. in thickness. Two series of sections 

 were swelled in a dark room at 16 C., with the following results: 



TABLE 13. 



p. ct. p. ct. 



Water 1,400 1,025 



Potassium nitrate, 0.01 N 900 800 



Potassium nitrate, citric acid, 0.01 N 650 675 



Potassium nitrate, 0.01 N 850 750 



Potassium citrate, citric acid, 0.01 N 725 .... 



Citric acid, 0. 01 N 700 625 



Sodium hydroxid, 0.01 M 1 , 000 925 



The action of this mixture fixes attention by reason of the extra- 

 ordinarily high amount of swelling in the alkaline solution. The 

 amount of swelling in acid does not average more than half that in 

 distilled water. The behavior of nucleinic acid and of peptone when 

 mixed with agar is such as to suggest that a study of the action of 

 these substances when combined separately and together with agar 

 would be of interest in connection with interpretations of nuclear 

 phenomena. 



The series of tests now including some data from mixtures of most 

 of the albumin and protein derivatives which were available, it was 

 deemed advisable to introduce more than one nitrogenous compound 

 into the biocolloid. The first mixture contained 90 parts agar, 3 parts 

 nucleinic acid, 3 parts peptone, and 4 parts of asparagine. The plates 

 dried to a thickness of 0.2 mm. and sections were swelled in a room 

 at 15 C. with the results as given in table 14. 



The outstanding features in table 14 are the comparatively high 

 amount of swelling in the salts. The expected high hydration in acid 

 solutions is not exhibited. 



