270 



SCIENCE 



[N. S. Vol. SLVI. No. 1185 



be considered. Certain of tli,ese compounds 

 are invariably present, althougli in varying 

 concentration, and any attempt to apply 

 studies of imbibition to swelling and growth 

 problems must take into consideration the 

 fact that the various reactions due to the 

 presence or proportion of nitrogenous com- 

 pounds, alkalinity or acidity, invariably ensue 

 in saline solutions, attenuated as they may 

 be in young protoplasts. Tests were there- 

 fore planned to determine the action of the 

 common bases and acids on bio-colloids. 



Agar which has been used to represent the 

 carbohydrate constituent of living matter 

 gave the following results when dried plates 

 .28 mm. in thickness were tested: 



The amount of swelling as compared with 

 distilled water was decreased by both salts 

 and the inhibiting action increased with the 

 concentration. 



A mixture of 90 parts agar and 10 parts 

 of glycocoU gave the following swellings: 



From which may be seen that an inhibiting 

 effect on imbibition in the bio-colloid similar 

 to that of agar was exerted by these salts, the 

 effect increasing with the concentration and 

 the least swelling taking place in the calcium 

 compounds. 



A mixture of 90 parts agar and 10 parts of 

 peptone gave the following swelling measure- 

 ment. 



2076% 



Potaaalum Chloride, 

 Potassium Chloride Hydrochloric Acid 

 it//100 i»//100 



1230.8% 500% 



The lessening or inhibitory effect is seen 

 to increase with the concentration, and less 

 swelling takes place in equivalent calcium 

 solutions than in potassium. The irregular- 

 ities, however, suggest that peptone mixtures 

 present some special characters which will 

 need further analysis. 



Dried plates of a mixture of 90 parts agar 

 and 10 parts urea gave the following swelling 

 measurements : 



These results are in general accord with 

 those obtained from other nitrogenous mix- 

 tures. 



A mixture consisting of 10 parts of gelatine 

 and one part of mucilage from Opuntia might 

 be considered as equivalent to the colloids 

 consisting of 90 parts gelatine and 10 parts 

 agar, and gave the following swelling meas- 

 urements. 



