PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 547 



ency to swell at higher temperatures may be a peculiarity of cer- 

 tain colloids independent of any physiological activity. It may 

 be supposed, therefore, that the colloids of frog's smooth muscle 

 tend to swell at higher temperatures and that this tendency is, 

 at any rate at first, sufficient to overcome any tendency toward 

 loss of fluid which may be produced by more rapid lactic acid 

 formation at the higher temperature. 



The fact that the smooth muscle lengthens at the same time 

 that it swells in the Ringer solution at the higher temperature 

 shows that high temperatures must produce in the tissue some 

 change other than that which follows stimulation and results in 

 shortening. And it is interesting to remember in this connection 

 that the tendency to lengthen at temperatures above 40° is not 

 a general characteristic of smooth muscle. Vincent and Lewis 

 have shown that in mammalian smooth muscle heating produces 

 shortening somewhat as it does in striated muscle.''' It would be 

 difficult to believe that heating produced chemical changes of aii 

 opposite character in frog's muscle and in mammalian muscle; but, 

 if it may be supposed that heating produces in both tissues a tend- 

 ency for the colloids to swell and at the same time a tendency 

 toward lactic acid production, it would be easy to explain the 

 opposite reactions of the two tissues by supposing that in frog's 

 muscle the former change preponderated; and in mammalian 

 muscle, the latter. 



GENERAL CONCLUSIONS 



This article may be concluded by the statement of certain views 

 regarding the physiology of muscle and of muscular contraction 

 which are indicated or confirmed by the experimental results 

 which have been presented. 



Striated muscle consists of fibers surrounded by semi-permeable 

 membranes. The fibers are made up of sarcostyles and sarco- 

 plasm; the sarcostyles are fibrils with a characteristic structure 

 which run longitudinally through the fiber and are separated 

 from each other by the fluid sarcoplasm. The sarcostyles are 

 not separated from the sarcoplasm by semi-permeable membranes; 



" Vincent and Lewis; Jour. Physiol., 1901, vol. 26, p. 445. 



