542 EDWARD B. MEIGS 



General physiology of striated and smooth muscle 



The changes of length undergone by the smooth muscle fibers 

 in the various solutions which have been experimented with, 

 indicate that the structure of these fibers is such that any increase 

 in their volume brings about an increase in their length. It 

 must be pointed out that this conclusion and the others which 

 have been reached concerning the osmotic properties of both 

 striated and smooth muscle accord very well with certain earlier 

 work on the histology and physiology of the two kinds of muscle. 



The histological examination of striated muscle shows that 

 it has a rather complicated structure. The smallest visible 

 microscopic elements are the fibrillae or sarcostyles, which are 

 bundled together to form the muscle fibers. The volume of these 

 is made up to about equal parts of the sarcostyles and of the 

 spaces between them, which are filled with a medium probably 

 fluid called sarcoplasm. The muscle fiber is surrounded by a 

 histologically demonstrable membrane, the sarcolemma. Between 

 the muscle fibers are spaces filled with lymph. 



Histological examination of vertebrate smooth muscle has 

 shown that its so-called fibers cannot be regarded as bundles of 

 smaller elements comparable to the striated sarcostyles. The 

 fresh fibers, appear homogeneous'^ and the fixed fibers show little 

 more sign of inner structure than does any piece of coagulated 

 protoplasm. 3^ 



It is now well established that in fixed contracted specimens 

 of striated muscle the sarcostyles are relatively larger and the 

 sarcoplasmic spaces smaller than in uncontracted specimens; 

 while in fixed contracted preparations of smooth muscle the fibers 

 are relatively smaller and the interstitial spaces relatively larger.'^ 

 The author has advocated the view that these facts mean that 

 fluid passes from the sarcoplasmic spaces to the sarcostyles in 



*^ Engelmann; Archiv fiir die gesammte Physiologie, 1881, Bd. 25, p. 546. 



'^ Meigs; American Jour. Physiol., 1908, vol. 22, pp. 482, et seq. 



5^ See Hurthle; Biologisches Centralblatt, 1907, Bd. 27, pp. 122-124; Meigs, 

 Zeitschrift fiir allgemeine Physiologie, 1908, Bd. 8, p. 81; American Jour. Physiol., 

 1908, vol. 22, p. 477; Gutherz, Archiv fiir mikroskopische Anatomie und Entwickel- 

 ungsgeschichte, 1910, Bd. 75, p. 209; Heiderich; Anatomische Hefte, 1902, Bd. 19, 

 p. 451; Eycleshymer, Am. Jour. Anat., 1904, vol. 3, p. 293. 



