430 



SCIENCE 



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



gadro's law is illustrated by tlie following 

 experiment. 



In an m/8 solution of NaCl 85 per cent, 

 of the molecules are dissociated into ions. 

 If we want to prepare solutions of non- 

 conductors (e. g., sugars) of the same os- 

 motic pressure as an m/8 NaCl we must 

 choose a concentration of .231m. At a 

 concentration of a sugar solution of .200m 

 a muscle must absorb water, while at a 

 concentration of .250 and above it must 

 lose water. We have made this experi- 

 ment for three sugars, a mono-saccharide, 

 grape sugar; a disaccharide, cane sugar; 

 and a trisaccharide, raffinose. The follow- 

 ing table gives the change in weight of the 

 muscle in these solutions in one hour. 



The turning point between loss and gain 

 of weight lies for all those sugars between 

 the same limit of molecular concentration, 

 namely, between .2 and .25m ; and the most 

 important fact is that the value for the 

 three different sugars lies between the 

 limits calculated on the assumption that 

 the exchange of water between muscle and 

 surrounding solution is determined by 

 Avogadro-van't Hoff's law. As long as 

 we are dealing in biology with only quali- 

 tative results there may always be some 

 doubt in regard to the applicability of 

 such a law to a life phenomenon, but if the 

 results come out quantitatively identical 

 with those calculated we may be pretty 

 sure that the law holds good for these cases. 



Miss Cooke^ investigated in the writer's 

 laboratory the gain of weight in the muscle 

 in hypotonic and hypertonic NaCl solu- 

 tions. Near the isotonic point the amount 



'Journal of Physiology, Vol. 22, p. 137, 1898. 



of water increases at first slowly in almost 

 a straight line with the dilution ; but as the 

 solutions become more dilute the amount 

 of water taken up increases at a rate far 

 gTeater than the rate of dilution of the 

 solution. Miss Cooke points out that this 

 may be due to some secondary change in 

 the muscle caused by the dilute solution 

 or the entrance of water into the muscle. 

 In hypertonic solutions irregularities were 

 noticeable, due probably to the varying 

 condition of rest or activity in the indi- 

 vidual muscle before the experiment. 



The following gives a series of deter- 

 minations in equi-molecular solutions of 

 NaCl and cane sugar, by R. Webster." 



CHANGE IN WEIGHT OP FROG'S GASTROCNEMIUS 

 AFTER ONE HOUR IN EQUI-MOLECULAR SOLU- 

 TIONS OF NaCl AND CANE SUGAR. 



While the gain in weight of the muscle 

 in the equivalent hypotonic solution is 

 practically the same in NaCl and cane 

 sugar, in the hypertonic solutions of cane 

 sugar the muscle loses more than in the 

 equi-molecular solutions of NaCl. This is 

 probably due to the fact that solutions of 

 cane sugar have an abnormally high os- 

 motic pressure and that this anomaly seems 

 to be more pronounced the higher the con- 

 centration. 



The number of animal organs in which 

 the applicability of Avogadro's law can be 

 tested is limited, since for this purpose it 

 is necessary that the tissues have no pores 

 or capillary spaces in which the surround- 



"E. Webster, University of Chicago Decennial 

 Publications, Vol. X., p. 105, 1902. 



