192 PHYSIOLOGY iBoT. Absts., Vol. VII, 



1291. MacDougal, D. T., and H. A. Spoehr. The components and colloidal behavior of 

 plant protoplasm. Proc. Amer. Phil. See. 59: 150-170. 1920. — The authors give summarized 

 statements of investigations on biocolloids previously published. Newly obtained results 

 are given for (1) the proportions of carbohydrate and albuminous matter in a colloid of the 

 highest hydration capacity; (2) the substances or ions of biological significance which would 

 raise the hydration capacity of these phytocolloids to the highest limit; (3) measurement of 

 the relative effects of some metallic bases upon a carbohydrate colloid; and (4) determina- 

 tion of the amplitude and continuance of alternating or repeated eiJects of renewed or replaced 

 solutions. The highest swelling of pentosan-protein mixtures is that of agar 1, gelatine 3, 

 in hundredth normal acid; such colloids are, however, unusual in the plant. Colloids in 

 which the carbohydrate and albuminous components each vary in forming 30-60 per cent 

 of the total and showing high hydration capacities in the hydroxides, in glycocoll and in 

 water, furnish an analogue of living matter of proved similarity of composition and action. 

 Biocolloids containing more carbohydrate than albuminous matter would be most sensitive 

 to the presence of hydrogen ions, and their growth would be markedly limited by acidity. 

 All types of biocolloid would respond by increased hydration to the presence of amino acids, 

 as shown by relative swellings in glycocoll and in histidine. Mixtures consisting of 40-60 

 per cent of the two main components are seen to give the highest swelling values in histidine 

 yet obtained for biocolloids by treatment with any reagent. Alkaline hydroxides may cause 

 a swelling of agar greater than in water, as in the case of experiments with amino acids. The 

 stronger the base as indicated by its position in the electromotive series, the more it restricts 

 hydration. The inclusion of a substance or ion in a colloidal structure results in hydration 

 relations of a different character from those which appear when the substance in question is 

 presented in the hydrating solution. Unequal expansion in all directions of dried sections of 

 colloids when immersed in solutions was again observed. — Wanda Weniger. 



DIFFUSION, PERMEABILITY, ADSORPTION 



1292. Andr^:, G. Sur I'exosmose des principes acides at sucres de I'orange. [Exosmosis 

 of the acids and sugars of the orange.] Compt. Rend. Acad. Sci. Paris 170: 1199-1203. 1920. 

 — A comparison is made of the rate of diffusion of acids and sugars through the cells of 

 intact quarters of oranges immersed in distilled water and in sugar or salt solutions respec- 

 tively. Sugar and acid are found to leave the cells in about equal proportions, the ratio of 

 sucrose to reducing sugars remaining approximately constant, though a considerable inversion 

 of sucrose occurs during exosmos s. — C. H. Farr. 



1293. Bradford, S. C. Adsorptive stratification in gels. Biochem. Jour. 14: 29-41. 

 PL 2. 1920. 



1294. Bradford, Samuel Clement. Adsorptive stratification of gels. IV. Biochem. 

 Jour. 14:474-482. PI. 7-8, 1 jig. 1920. 



1295. Lloyd, Dorothy Jordan. On the swelling of gelatin in hydrochloric acid and 

 caustic soda. Biochem. Jour. 14: 147-170. 7 fig. 1920. 



1296. Stiles, Walter. I. The penetration of sodium chloride into gels of agar-agar, 

 containing silver nitrate. Biochem. Jour. 14: 58-72. 4 fis- 1920. — Agar containing silver 

 nitrate is employed as the gel, and the progressive penetration of sodium chloride is observed 

 by the precipitation of silver chloride. Such penetration is found, within wide limits, to be 

 proportional to the square root of the time and is a constant for any particular gel and any 

 particular concentration of penetrating salt. The rate of penetration depends upon (1) the 

 initial concentration of the penetrating salt, and (2) the concentration of silver nitrate. The 

 concentration of the gel has little influence. An empirical relation is found between pene- 

 tration, time, and penetrating salt. — Alva R. Davis. 



