520 EDWARD B. MEIGS 



experimenting with isotonic KCl solution ^I have found that it 

 does not kill frog's striated muscle even in several hours at tem- 

 peratures below 18°. It takes the muscle a good deal longer to 

 recover in Ringer's solution after immersion in KCl than after 

 immersion in K2HPO4, but the recovery does take place in time 

 very completely, even though the swelling in the KCl solution 

 may have amounted to 50 per cent of the original weight of the 

 muscle (Experiments 64, 66, 72, 74 and 77). 



The membranes surrounding the fibers of striated muscle must, 

 therefore, be regarded as quite permeable to KCl, and this would 

 seem to make it difficult to generalize about their chemical 

 nature. They must differ in an interesting way from the mem- 

 branes surrounding the red blood cells, which are notably imper- 

 meable to KCl. 23 The permeability of the muscle membranes to 

 KCl may play an important part in the maintenance by the fibers 

 of their normal potassium content. 



Experiments with solutions of non-electrolytes. One of the 

 strongest reasons for believing that the fibers of frog's striated 

 muscle are surrounded by semi-permeable membranes, is the fact 

 that the tissue maintains its original weight for many hours in 

 isotonic solutions of sugar, gains weight in hypotonic solutions, 

 and loses weight in hypertonic solutions of this substance. Over- 

 ton has tried the effect of immersing the tissue in isotonic solu- 

 tions of various sugars and of a number of other non-electrolytes. 

 He finds that it maintains its original weight in isotonic solutions 

 of sugars and of amino acids, ^^ but gains weight more or less rapidly 

 in isotonic solutions of glycerine and urea.^^ He concludes that 

 the muscle membranes are permeable to the last two substances 

 and impermeable to the others. 



I have followed the weight changes undergone by smooth mus- 

 cle in isotonic solutions of cane sugar, lactose, dextrose and alanin. 

 The tissue gains weight rapidly in all of these solutions (figs. 9, 



" Hamburger; Osmotischer Druck und lonenlehre, Wiesbaden, 1902, vol. 1,'pp. 

 208 and 209. 



2* Overton; Archiv fur gesammte Physiologie, 1902, Bd. 9*2, pp. 215, 224, 233; 

 see also pp. 352-357. 



« Loc. cit., pp. 197, 198 and 205-207. 



