PHYSIOLOGY OF SMOOTH AND STEIATED MUSCLE 513 



of the smooth muscle fibers ara quite permeable both to the mus- 

 cle salts and to the salts of Ringer's solution. 

 . Overton has pointed out^o that the behavior of muscle in non- 

 isotonic solutions may better be studied after the tissue has been 

 kept for some time in a nearly isotonic solution. It will be seen 

 that this procedure presents difficulties in a comparison of smooth 

 with striated muscle; the two tissues from the same frog hardly 

 ever maintain the same weight in any salt solution. I have, 

 however, overcome this difficulty as far as possible by using 

 the tissues both of those frogs of which the smooth muscle swells 

 markedly in Ringer and of those of which it does not. There 

 is no important difference in the results obtained in the two cases. 



TERCE/ITAQE 

 CHA/1QE. 1/1 WEIQHT 



MOURvS / 2 3 ^ J 



Fig. 2 Changes in weight undergone by two pieces of the stomach muscle of 

 a frog; of which one (broken line) was immersed in Ringer's solution at between 

 20° and 21°, and the other (unbroken line) in Ringer's solutions at between 0° 

 and 1°. See Experiments 19 and 20. 



Smooth muscle has another peculiarity which must be taken 

 account of in the experiments to be described. If a piece of the 

 tissue be placed in Ringer and weighed at long intervals, say every 

 half hour, it will be found that its change in weight takes a cer- 

 tain line. But, if at the end of an hour or so the weighings be 

 suddenly increased in frequency to once in five or ten minutes, 

 the tissue may begin to lose weight rapidly and continue to do so 

 through several weighings. The same thing is true to a very much 

 less extent for striated muscle. Figure 3 shows the difference in 

 the effects of increasing the frequency of weighings and dryings in 

 the two tissues. 



20 Overton; Archiv fiir die gesammte Physiologic, 1902, Bd. 92, p. 128. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 4 



