MacDOUGAL— HYDRATION AND GROWTH. 351 



Two groups were chosen for the tests. Succinic acid and amino- 

 succinic or aspartic, which are dibasic, and its amide as noted above 

 which is monobasic, and acetic acid and amino-acetic or glycocoll, 

 which are monobasic. Sections of plates of agar, gelatine, agar- 

 gelatine, agar-protein and other mixtures were used. Swellings 

 were carried out in the equable temperature chambers of the Coastal 

 Laboratory at 15-16° C. A tabulation of the principal results is 

 given on the following page. 



The two organic acids, succinic and acetic, are seen to exert the 

 classical effect on gelatine, the greatest hydration taking place in 

 the higher concentrations, the effect decreasing with dilution until 

 at 0.0004 ^ the swelling in acetic acid was scarcely greater than in 

 distilled water. At 0.0004 M however the dibasic succinic acid 

 showed a swelling less than that in distilled water, a fact which sug- 

 gests a rapid solution or dispersion from the surfaces of the sections 

 and alterations of viscosity in the mass. 



Mixtures of agar (8) and gelatine (2 parts) were now tested, 

 and the hydration in succinic at 0.00008 M was but 1030 per cent, 

 as compared with 1684 per cent, in water, while acetic acid was 

 slightly higher, 1167 per cent. A similar statement would hold for 

 the action of these acids on agar, and for agar-protein, the hydration 

 of water along being reached more nearly than in the agar-gelatine 

 sections. 



When we now turn to amino-succinic or aspartic acid and amino- 

 acetic acid or glycocoll, some new relations are uncovered. 



The aspartic acid (amino-succinic) appeared to exercise a notable 

 influence on the hydration of agar within the range of its solubility. 

 When more than this was added to the water used for solution a 

 swelling in excess of the expectancy resulted. It was also seen that 

 the surface of the liquid became covered with thin crystals. In all 

 probability the solution or dispersion of some agar into the water 

 resulted in the displacement of some of the acid with the result that 

 the sections were actually hydrated from a solution less concen- 

 trated, giving a swelling in excess of the expectancy. 



Asparagin was now applied in a series of concentrations to sec- 

 tions of agar of the above swelling capacity in water and it was 

 found that hydration was actually increased or accelerated by the 



