142 



SCIENCE 



[N. S. Vol. XL VI. No. 1180 



Cornell University Medical College, 'New York 

 City. The accomplisliment of a given amount 

 of mechanical v7ork is always at the expense 

 of a given amount of energy and the amount 

 of energy required for the mechanical work is 

 independent of the physical condition of the 

 subject and of the quantity of carbohydrate 

 present in the gastrointestinal tract. 



Report of the annual meeting: Award of 

 medals, research grants from the trust funds. 

 Edwin BrowELL Wilson 



Massachusetts Institute of TECHNOLoaT, . 

 Cambridge, Mass. 



SPECIAL ARTICLES 



NOTE ON THE SWELLING OF GELATINE AND 



AGAR GELS IN SOLUTIONS OF 



SUCROSE AND DEXTROSE 



The tests reported in this note were made 

 incidentally in connection with experiment3 

 by D. T. MacDougal^ on the swelling of cactus 

 tissues (Opuntia) and of certain artificial gels 

 in water and in dilute solutions of acids and 

 alkalis. The method was the same in all par- 

 ticulars as that described by MacDougal. 

 Small plates cut from thin, dried sheets of 

 the various gelatine-agar mixtures were 

 placed in the sugar solutions and the increases 

 in thickness which occurred as these plates 

 imbibed water and swelled were measured by 

 the auxograph. The experiments were at room 

 temperature, which ranged between 60° and 

 70° F. (16° and 21° C). In all cases the gels 

 were the identical preparations used by Mac- 

 Dougal. The sucrose was the usual " c. p." 

 grade. The dextrose was Merck's " highest 

 purity." The sugar solutions were tested for 

 neutrality to phenolphthalein and litmus. 

 Sugar concentrations are in percentages by 

 weight. 



The results are given in the following tables 

 as percentage increases in thickness of the 

 gel plates after approximately 12 hours in the 

 respective solutions. The original thicknesses 

 were measured by a micrometer gauge. Pre- 

 liminary tests for longer time periods indi- 

 cated that the swelling was always complete 

 or very nearly so, in 12 hours. In the tables, 



1 Science, N. S., Vol. XLIV., pp. 502-505, 1918. 



figures on a single horizontal line represent 

 tests made at the same time and under sub- 

 stantially identical conditions, the only differ- 

 ences being between the concentrations of the 

 sugar solutions. 



EXPERIMENTS WITH SUCROSE 



Gelatine (without Agar) 



EXPERIMENTS WITH DEXTROSE 



Gelatine (without Agar) 



Gelatine 80 — Agar SO 



