470 STUDIES IN GENERAL PHYSIOLOGY 



in weight occurs more slowly than the increase in the con- 

 centration of the external solution. 



Both results point to the fact that an increase works in 

 the same sense as a decrease in the amount of water con- 

 tained in the cells, for both lead, apparently, to an increase in 

 the osmotic pressure within the cells. 



It is generally stated that muscles always twitch in con- 

 centrated salt solutions in consequence of the loss of water 

 which they suffer, and Miss Cooke was inclined to see in 

 these twitchings the cause of the increase in the osmotic 

 pressure in the muscles immersed in hyperisotonic salt solu- 

 tions. I noticed, however, that these twitchings always 

 occurred in 1.05 and 1.4 per cent, solutions; that they occur- 

 red only rarely in 1.7 per cent, solutions, and that they 

 never occurred in 2-2.8 per cent, solutions. It is possible 

 that they occurred in the latter case only during the first few 

 moments after immersion and then ceased. They might in 

 this way have escaped my notice. One cannot, therefore, 

 simply say any longer that the withdrawal of water brings 

 about contractions in the muscle, but one must add that this 

 occurs only when the difference in osmotic pressure between 

 the outer solution and the muscle is not too great, or, perhaps 

 more accurately, when the concentration of the surrounding 

 solution is not too high. 



The fact that the loss of water by the muscle increases 

 more slowly than the difference in the osmotic pressures 

 between the outer solution and the muscle is supplemented 

 by the behavior of the muscle when left for a long time in 

 0.7 per cent, and hyperisotonic sodium-chloride solutions. 

 The decrease in weight soon comes to a standstill, and the 

 muscle begins to take up water so that in eighteen hours its 

 weight is greater than its original weight. This occurs even 

 when the muscle is kept in a 2.8 per cent. NaCl solution! 



This fact that the "injured" muscle is able to take up 



