PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 529 



portions of these tissues are surrounded by semi-permeable mem- 

 branes. The changes of weight undergone by smooth muscle 

 and tendon in various solutions bear only a rough relation to the 

 osmotic pressures of the solutions, and are in all probability 

 analogous to the changes of weight undergone by gelatin and 

 fibrin under similar conditions. The differences in the behavior 

 of smooth and striated muscle in the solutions used always show 

 themselves long before either tissue has permanently lost its 

 irritability. Under all the conditions so far tried the smooth 

 muscle remains alive longer than the striated ; and the reactions 

 of the former must therefore be regarded as, if anything, more 

 'normal' than those of the latter. 



CHEMICAL EXPERIMENTS ON THE DIFFUSION OF SALT AND SUGAR 

 THROUGH THE SURFACES OF THE SMOOTH MUSCLE FIBERS 



The experiments on the changes of weight undergone by smooth 

 muscle in various solutions should be supplemented by numerous 

 others which will demonstrate directly by chemical analysis that 

 salts and sugars diffuse through the surfaces of the living smooth 

 muscle fibers; and by still others which will throw light on the 

 sources of the potassium and phosphorus found in the smooth 

 muscle ash. I hope to carry out such experiments in the not 

 distant future. But such chemical experiments demand a great 

 deal of time and material; it will, perhaps, be proper to give in 

 this place some preliminary results from work in this field. 



Experiments 58, 59, 62 and 63 give the results of an attempt to 

 determine directly whether potassium, sodium, and cane sugar 

 diffuse through the surfaces of the living smooth muscle fibers. 

 Experiments 58 and 59 show that something more than 40 per 

 cent of the tissue's sodium diffuses out into a surrounding sugar 

 solution in five hours. The volume of such samples of tissue as 

 were used in Experiments 58, 59, 62 and 63 consists to about 85 

 per cent of muscle fibers and to about 15 per cent of connective 

 tissue and interstitial spaces. If the connective tissue and inter- 

 stitial spaces be supposed to contain NaCl in the same concen- 

 tration as the blood plasma," the amount of the salt in these parts 



" See Urano: Zeitschrift fiir Biologie, 1907, Bd. 50, pp. 218, 219, 224 and 225. 



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



