OBSERVATIONS ON STRIPED AND UNSTRIPED MUSCLE. 95 



gold and formic acid in the usual way. Mauy fibres were thus 

 obtained completely contracted and also many fixed waves of 

 contraction. 



I also made preparations of relaxed muscle from a Dytiscus 

 killed with chloroform. However, as the fibres vary so much 

 in appearance according as they are more or less pressed out 

 in the gold preparation, comparisons of the muscle stimulated 

 with alcohol vapour, with that reduced by chloroform, though 

 they may give the general effect of the difference, are not abso- 

 lutely trustworthy. The only way of really proving this point 

 is to examine a fibre, one portion of which is in the relaxed 

 condition and the other contracted, or, in other words, a fixed 

 wave of contraction. 



On careful examination of the network in one of these fixed 

 waves of contraction with the y^- immersion objective the longi- 

 tudinal fibrils of the network were always straight in all 

 parts of the fibre and appeared slightly thicker in the 

 contracted part of the fibre although it was difficult to judge 

 accurately of the difference in thickness. The nodal dots, 

 however, were the same size in both the contracted and 

 relaxed portions of the fibre. The dots appeared in many 

 cases even smaller in the contracted than in the relaxed muscle. 

 This is, I believe, due to their being more separated from each 

 other laterally, whereby the refractive effects which somewhat 

 obscure the real size of the dots in the relaxed muscle are 

 diminished (fig. 14). 



It therefore appears from gold preparations that during con- 

 traction the nodal dots do not alter in size but that the longi- 

 tudinal bars of the network increase in thickness. The apparent 

 enlargement of the nodal dots when the fibre is seen in the 

 fresh state is due to optical effect. Moreover, if the nodal dots 

 do not alter in size it follows necessarily that the longitudinal 

 bars must increase in thickness ; for since they keep straight 

 during contraction if they do not increase in thickness there 

 must be a diminution in the volume of the fibre, which is known 

 not to occur. 



These results differ from the account given by S chafer of the 



