ORGANISATION AND STRUCTURE OF MUSCLE 



49 



duced in 

 during the 



It is also easy to see that ' the dark, sharply defined 

 bands appear where the relaxed muscle presents the segments, 

 (JZJ}, or (JNE, Z, E NJ), and that the light bands correspond 

 essentially with the contracted strias (Q h Q). 



The muscle-fibres of insects, killed by strong alcohol, often 

 exhibit local contractions (" fixed waves of contraction ") in which 

 the histological changes pro- 

 the striated fibrils 

 transition from rest 

 to contraction can be ascer- 

 tained exactly by means of 

 staining methods and reagents. 

 These very subtle manifestations 

 are of the greatest theoretical 

 interest, and must be discussed 

 a little more fully. 



As before, we may accept 

 the penetrating conclusions of 

 Eollett (22). On examining a 

 well-fixed wave of contraction, 

 from a fibre of Otiorlnjnclius 

 mastix stained with haematoxy- 

 lin (Fig. 31), it is in the first 

 place evident that the dark-blue 

 band (C) of the contracted por- 

 tion of the fibre, Nasse's " con- 

 traction-disc," is derived from 

 the transformation of the system 

 (JNE,Z,ENJ), and is there- 

 fore the same section which 



__ 



Engelmann denotes as isotropous, 

 and Eollett as the arimetabolous 

 layer (a). 



In the relaxed arimetabolous layers the bands (Z} and (N] are 

 deeply stained, the bands (E} and (J) not at all, or very slightly ; 

 in the relaxed " metabolous " sections (Q h Q) (Engelmann's 

 " anisotropous " layer), which Eollett denotes by //,, the ends of 

 Q are more deeply stained than the centre h (Hensen's stripe). 

 With increasing contraction of the section (a), the diminishing 

 bands (N~) draw nearer and nearer to (Z), until at last the two 



E 



iMtimmttttmir 



>* *>*<>** 



/ _ ,.'. T-jt i i) -111 rrv -,- frt jji j^ jjj< _^ Jj. _^ ^ !^t j.j.'j t -^- i-u^ ff 



,*'*** 



' 



y 

 c 



Q' 

 C 



Fio. 31. Muscle -fibre of Otiorhynchns mastix, 

 showing wave of contraction. (Rollett.) 



;*** t( 



' *' 



