432 



SCIENCE 



[N. S. Vol. XXXVII. No. 951 



matter whether molecules are small or 

 large, light or heavy. 



Can we not suppose under these circumstances 

 that there is no limit of size for the particles 

 which obey this law? Should it not be possible 

 that even visible particles obey this law exactly, 

 so that a granule, agitated by brownian move- 

 ment, counts neither more nor less than an ordi- 

 nary molecule in regard to the action of its shocks 

 on a wall which blocks its progress? Or, in other 

 words, may we not assume that the laws of per- 

 fect gases can be applied to emulsions made of 

 visible granules." 



It is well known that Perrin determined 

 the value of N from the measurement of 

 the relative distribution of the suspended 

 particles of an emulsion of mastix in a 

 vertical column and found iV = 62.2.10--. 

 Almost identical values were obtained by 

 him by three other methods. This proves 

 that as far as osmotic pressure is concerned 

 the suspended particles of an emulsion 

 behave exactly like the molecules of a gas. 



Direct osmometric measurements of the 

 osmotic pressure of proteins gave very low 

 figures, as was to be expected from their 

 high molecular weight. R. S. Lillie found 

 30 to 40 mm. Hg for a 2 per cent, solution 

 of albumen,^- Starling for the proteins of 

 blood serum 40 mm. Hg. 



The question may now be asked whether 

 or not the proteins in solution have other 

 qualities by which they attract water than 

 their osmotic pressure? This question can 

 easily be answered by using living cells 

 as osmometers. We have seen that an 

 m/8 NaCl or a .231m sugar solution are 

 isotonic with a frog's muscle (gastroc- 

 nemius). The latter solutions have an 

 osmotic pressure of 3933 mm. Hg. "We 

 have also seen that as an osmometer a 

 frog's gastrocnemius may be considered 

 accurate at the point of isotony within 

 .03m sugar. Hence the osmotic pressure 



" Perrin, ' ' Les Atomes, ' ' Paris, 1912, p. 128 fl. 

 "LUlie, Am. Jour, of Physiol., Vol. 20, p. 197. 



of the proteins of the blood is below the 

 limit of sensitiveness of the muscle as an 

 osmometer ; or, in other words : if the at- 

 traction of water by blood is determined 

 solely by the osmotic pressure of the blood 

 that part of its total osmotic pressure 

 which is furnished by the proteins must be 

 negligible. This is indeed the case. 



I asked my assistant, Dr. Beutner, to 

 compare the change in weight of a frog's 

 muscle in various solutions with and with- 

 out proteins.^^ 



The differences in the two rows of figures 

 are slight in comparison with the experi- 

 mental errors and show that the addition 

 of gelatine does not influence noticeably 

 the absorption of water. 



In a second experiment it was ascer- 

 tained that in blood serum which was 

 freed from the greater part of its salts by 

 dialyzing it for 40 hours through parch- 

 ment paper the muscle gains exactly as 

 much in weight as it does in a NaCl solu- 

 tion of the same osmotic pressure. The 

 serum had after dialyzation a freezing 

 point depression of .03°, corresponding to 

 a concentration of NaCl of about m/120. 



CHANGE IN WEIGHT OP TWO GASTEOCNEMII OF 

 THE SAME FBOG 



Muscle a in Muscle 6 in 



Dialyzed Serum, m/120 Ringer, 



Per Cent. Per Cent. 



After i hour ... + 22.3 + 24.7 



After 1 hour ... -|- 34.0 -f- 88.0 



After 2i hours . -|- 51.0 4-53.6 

 " E. Beutner, Biochemische Zeitschr., Vol. 48, p. 

 217, 1913. 



