PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 



545 



the sarcostyles to swell; and in smooth muscle, by causing the 

 fibers to lose fluid. Experiments 23, 28, 39 and 44 show how the 

 production of lactic acid might bring about both sets of results. 

 It has long been known that striated muscle swells in weak 

 acid solutions, and this fact has been vaguely taken to mean that 

 tissues generally swell in such solutions. It is now well known, 

 however, that striated, muscle may produce large amounts of lac- 

 tic acid on its own account when placed under abnormal condi- 

 tions, and it is impossible to distinguish the swelling produced 

 by the external acid from that caused by the muscle's own yield. 



rERCEy^TAOtCHA/Kii: 



(<7 



ninuTE5 



fo io fo to H 



Fig. 20 Changes in weight undergone by a living sartorius (broken line) and 

 by a dead sartorius (unbroken line) in 7.5 per cent cane sugar solution. See Exper- 

 iments 5 and 6. 



The experiments with connective tissue furnish the possibihty of 

 determining how strong an acid solution must be before it can pro- 

 duce swelling in this tissue, and they show that the same concen- 

 tration of acid which promotes swelling in the connective tissue 

 inhibits it in the case of the smooth muscle. 



It may be, then, that stimulation causes smooth muscle to 

 produce very small quantities of lactic acid, and that the acid 

 production results in a tendency for the muscle fibers to lose fluid 

 and shorten. 



This would seem to contradict the general rule which has been 

 set up by the work of Wolfgang Ostwald, Lillie, Fischer and 

 others*^ ^q ^j^g effect that colloids tend to swell more in acids and 



" See Ostwald; Archiv fiir die gesammte Physiologie, 1905, Bd. 108, p. 563, Bd. 

 109, p. 277; Lillie, American Jour. Physiol., 1907, vol. 20, p. 127; Fischer, Archiv 

 fiir die gesammte Physiologie, 1908, Bd. 124, p. 69; Bd. 125, p. 99. 



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



