B 



Microns 



Figure 142. — Small pieces of four white fibers of the adductor of C. v'rginica seen under phase contrast lens. Whole 

 mounts of a preparation teased after treatment with nitric acid. Glycerol. A — completely relaxed fiber from nar- 

 cotized oyster; B — strongly contracted fiber; C — slightly contracted fiber; D — folded but not contracted fiber. 

 Figures B and D are from one preparation of a highly contracted adductor. 



concluded that the fibers of that part of the muscle 

 differ from true cross striated muscles in that the 

 bands (A and I) lie at about a 10-degree angle to the 

 fiber axis and are arranged helically around tlie 

 outer part of the fiber; this produces the double 



oblique striation visible in the light microscope. 

 Hanson and f^owy's observations were based on 

 electron microscopy, and tlie bands they refer to 

 as A and I are not visible under the light micro- 

 scope. 



THE ADDUCTOR MUSCLE 



155 



