Dwight.] 124 [Nov. 5, 



The most puzzling point of all is to decide at just what stage of 

 contraction the gray disappears. This is particularly difficult to ob- 

 serve, because the colors are changing their shades and positions at 

 the same time. It is certain that the gray has disappeared somewhat 

 early in the contraction — say in its first half, and also that it is not 

 the very first change, for it may be seen in very slightly contracted 

 fibres. There does not appear, at least in the detached leg, to be 

 any law regulating the direction of the wave; it seems quite acci- 

 dental whether it runs toward the tendon or from it. Usually it 

 begins at one end of a fibre, and after a moment's pause runs the 

 whole length, when it either dies out, or, as is more frequently the 

 case, returns, gradually growing weaker, and embracing less of the 

 fibre. When the specimen is fresh and lively, a wave of average 

 size comprises the substance between seven or eight bands, and as 

 long as contraction lasts, rarely less than that of three elements is 

 involved. As the wave runs toward the end of a fibre the part be- 

 hind it is put more or less upon the stretch, frequently enough so for 

 it to assume the condition already described as the third state. 

 When the contraction is nearly over, it is not rare to see the fibre 

 restored to its normal state by a sudden jerk in the direction opposite 

 to that pursued by the wave, evidently caused by the elasticity of 

 the stretched portion. The contractile force of the part of fibre in 

 action overcomes the elasticity of the part at rest, but at a certain 

 moment the latter property reasserts itself. 



Merkel, as already mentioned, describes a homogeneous appearance 

 as characteristic of a certain stage of contraction. Seh'afer, on 

 the other hand, thinks it occurs during perfect rest. For my part I 

 have never seen it at all. In beetles, however, that have suffered 

 from confinement, it is not very rare to find the markings very indis- 

 tinct, and in some cases many stray granules are found in the fibre, 

 particularly near the surface. I have often noticed the latter appear- 

 ance after the muscle had become exhausted by electricity. The 

 long muscle corpuscles, well described and represented by Klein, 1 are 

 often seen very near the surface of the fibre. In the living and 

 healthy muscle a longitudinal striation is almost never seen, though 

 it appears in unhealthy fibres. It is superficial, and probably exists 

 solely in the sarcolemma. 



The polariscope has been much used, in order to decide on the 

 differences of the nature of certain parts, but the results of different 



1 Handbook for the Physiological Laboratory. 



