290 COLLOIDS IN BIOLOGY AND MEDICINE 



Salts diminish the swelling of muscle in acids and alkalis in a way 

 similar to the case of fibrin and gelatin, though not so obviously. 



There is, indeed, a very important difference between dead and 

 living muscle: the swelling of dead muscle in distilled water, for 

 instance, is brought about by the formation of lactic acid, which sets 

 in within a few minutes. If this were not the case, a living frog would 

 swell up as much in fresh water as a dead one. 1 According to M. H. 

 FISCHER, a dead muscle retains its form in a 0.7 per cent NaCl solu- 

 tion, not because the same osmotic pressure exists inside and outside 

 the cell, but because the concentration of the NaCl solution is just 

 sufficient to overcome the action of the acids formed in the excised 

 muscle. We must again point out here that the experiments of W. 

 BILTZ and A. VON VEGESACK * show that if colloids are present in a 

 medium, the presence of isotonicity does not by any means permit us 

 to infer that equal osmotic pressures exist. 



Against M. H. FISCHER'S experiments, the objection has been 

 raised that dead muscle possesses no semipermeable membrane, so 

 that its swelling follows laws similar to those of fibrin, etc. In living 

 muscle, however, semipermeability exists; on this account the re- 

 sults of M. H. FISCHER cannot be transferred to living muscle. 

 There are also certain discrepancies in respect to some nonelectro- 

 lytes; thus, for instance, dead muscle does not swell up in iso tonic 

 sugar solution; this does not accord with FISCHER'S theory. [Sugar 

 has a specific dehydrating action. Tr.] 



The studies of E. B. MEIGS * have illuminated these discrepancies; 

 they showed a definite difference between smooth and striated muscles. 

 Smooth muscles are involuntary and occur in automatically acting 

 organs (intestines, urinary bladder, iris, etc.), and especially widely 

 distributed among the lower animals. They contract much more 

 slowly than striated muscles. E. B. MEIGS concludes that smooth 

 muscle is not surrounded by a semipermeable membrane, in other 

 words, osmosis is not a factor, but that they behave toward electro- 

 lytes like any hydrophile colloid, fibrin or gelatin, with reference to 

 change in volume. 



The behavior of striated muscles is quite different. To understand 

 it we must briefly recall their histology. Muscles consist of bundles 

 of fibrils, longitudinal fibers which are surrounded by a connective 

 tissue sheath. Each fibril, that is, every minute fiber, is surrounded 

 by a membrane, the sarcolemma, and is bathed in a fluid substance, the 

 sarcoplasm. The individual fibrils are striated at right angles to their 

 axes. The striations appear microscropically as alternating dark and 

 bright zones; while the latter are isotropic, the dark striations are 

 doubly diffractive, anisotropic (see Fig. 49). 



1 [If the circulation of a living frog is impeded so that local acidosis develops, 

 local swelling also develops. Tr.] 



