356 MacDOUGAL— HYDRATION AND GROWTH. 



A return was made to the biocolloidal mixtures and trios of sec- 

 tions of agar 8 parts and oat protein 2 parts with a thickness of .22 

 mm. were swelled at 18° C. The hydration swelling in the hun- 

 dredth normal acetic acid gave an increase of 13*18 per cent., while 

 an equinormal solution of the acetic acid and glycocoll gave a swell- 

 ing of 1605 per cent. This test is the only one of the series in which 

 the addition of glycocoll to the acetic acid enhances imbibition. 



An additional test was made in which equal amounts of gly- 

 cocoll and acetic acid were brought together at a concentration of 

 0.00 1 M on agar-oat protein sections as above. The swelling in the 

 acetic acid was 2681 per cent, or about the same as that possible in 

 distilled water (2630 per cent.) while the swelling in the combined 

 solution was slightly less, being 2570 per cent., a difference which 

 is without special significance in this case, as it is near the limit of 

 instrumental error or might have been caused by brief temperature 

 variations. 



The positive action of amino-compounds in affecting hydration 

 is well demonstrated by the above facts. These effects are not coin- 

 cident with the action of solutions offering the greatest hydrogen 

 ion concentration, or at any point in which an optimum of such 

 action might be assumed. The actual maximal hydrations in amino- 

 compounds take place in reality in attenuated solutions (o.i M to 

 0.00008^), but the nature of the action has not yet been determined. 



The Temperature Factor in Growth. 



If growth were dependent in the main upon any reaction or upon 

 a chain of consequent transformations the influence of temperature 

 upon the rate and course might be readily and definitely established. 

 Many authors have assumed such a state of affairs. 



Growth however is an interlocking mesh work of reactions and a 

 rise of temperature through the ordinary range from 5° C. to 30° C. 

 may and generally does pass the point at which one or more of the 

 reactions passes the range of its accelerating effect, and in any 

 further rise becomes an inhibition. Such results are to be found, 

 for example, in the action of hydrogen ions or in respiration res- 

 idues. The following experiments may serve to illustrate this 

 matter. 



