172 PROTOPLASMIC ACTION AND NERVOUS ACTION 



ably related to this peculiarity, but the nature of the 

 relationship is unknown. Recently Zwaardemaker has 

 attributed importance to the slight radioactivity of K, 

 on the ground of certain striking parallels between the 

 action of K salts and uranium salts on the frog's heart ;^ 

 but other evidence from experiments with marine 

 organisms fails to support this view.^ 



Recently Meigs^ has investigated the osmotic behavior 

 of smooth muscle in solutions of salts and non-electro- 

 lytes, and finds a number of remarkable differences 

 between this tissue and striated muscle. For example, 

 the stomach muscle of the frog gains weight when 

 immersed in isotonic solutions of sugar, alanin, or 

 NaCl, and even in Ringer's solution. He concludes 

 that smooth muscle cells differ fundamentally in their 

 structure and mode of action from striated muscle cells, 

 and that they are not surrounded by semi-permeable 

 membranes. In the adductor muscle of the marine clam 

 {Venus mercenaria), sl smooth muscle which reacts 

 slowly and maintains its state of tension for a long time, 

 closely similar conditions were found. Pieces of muscle 

 immersed in sea water take up chloride from the latter 

 and increase in weight; they even fail to lose weight in 

 lo per cent NaCl or in sea water of twice the normal 

 concentration. "* 



^ Zwaardemaker, Journal of Physiology, LIII (1920), 273, and 

 LV (1921), 33. 



^ R. F. Loeb, Journal of General Physiology, III (1920), 229. A. J. 

 Clark fails to confirm Zwaardemaker's claim that uranium can act 

 as a substitute for K in restoring the heartbeat (Journal of Pharmacology 

 and Experimental Therapeutics, XVIII [1922], 423), 



3 E. B. Meigs, Journal of Experimental Zoology, XIII (191 2), 497. 



4 Meigs, Journal of Biological Chemistry, XVII (1914), 81. 



