544 EDWARD B. MEIGS 



tions with surrounding solutions. Under these conditions a 

 change in the weight of the tissue as a whole would be much more 

 likely to mean a change in the volume of the sarcostyles than 

 under the conditions which exist while the tissue is still alive. 



It has been shown on pp. 532-535 of this article that changes of 

 length and volume run much more closely parallel in living smooth 

 muscle than in living striated muscle. This is easy to understand 

 if it may be supposed that changes in the length of the smooth 

 muscle fibers depend on exchanges of fluid between them and 

 their surroundings. 



Many aspects of the experiments which have been described in 

 this article acquire a new meaning in the light of these considera- 

 tions. Striated muscle immersed in distilled water first gains in 

 weight, then loses, then gains again, and finally loses again (fig. 

 16).^^ This peculiar behavior is readily explained by supposing 

 that the first gain is the expression of an osmotic intake of water 

 which results in the production of lactic acid and the destruc- 

 tion of the semi-permeable membranes. The lactic acid causes 

 the sarcostyles to swell slowly, but this swelling is more than off- 

 set in the second period of the curve by the loss of fluid from the 

 sarcoplasmic spaces. The second period of gain in weight is the 

 expression of the slow continued swelling of the sarcostyles after 

 the sarcoplasmic fluid has escaped; and the second period of loss, 

 of a slow loss of fluid by the sarcostyles due to the gradual escape 

 of lactic acid to the surrounding solution. Smooth muscle 

 immersed in distilled water simply gains and then slowly loses 

 weight ; it reacts as would the sarcostyles of striated muscle if 

 they were deprived of their surrounding sarcoplasm and semi- 

 permeable membranes (fig. 16). Attention may also be called 

 to the character of the curves which represent the swelling of 

 smooth muscle in distilled water and hypotonic solutions, and to 

 the manner in which the smooth muscle takes up fluid from solu- 

 tions of non-electrolytes. In all these particulars it resembles 

 dead striated muscle much more closely than living striated 

 muscle (figs. 3, 4, 5, 6, 9, 10, 11, 12, 14, 15, 16 and 20). 



It seems at first sight strange that the chemical processes which 

 bring about contraction should do so in striated muscle by causing 



*i See also Fischer, Archiv fiir die gesammte Physiologic, 1908, Bd. 124, p. 74. 



