476 



disk or sarcous element^). It is indeed clear that this must occur if 

 we compare the appearance of the contracted fibril (Fig. 3) with that 

 of the uncontracted fibril (Fig. 1) for in the former the isotropous sub- 

 stance has almost disappeared whilst the sarcous element or principal 

 disk is proportionately swollen. And it is probable that the isotropous 

 fluid has passed into the pores of the anisotropous disk, since these 

 pores are open on that side of the disk which is directed towards the 

 isotropous substance ^). 



^*7 



Fig. 1. Fig. 4. Fig. 3. 



So far I have dealt merely with observations concerning the fibrils 

 of the wing-muscles of insects, and the facts mentioned are in sub- 

 stance the same as those already published by me in the communi- 

 cations above referred to. These observations I have repeatedly had 

 occasion to confirm, but so far as I am aware, no other observer has 

 taken the pains to verify them, although if the wing -fibrils are em- 

 ployed, there is no difficulty in doing so ^). With the leg-muscles of in- 



1) This conclusion is supported b}'^ the observations of Bernard. 

 Zool. Jahrb., Bd. 7. 



2) Neither in the wing-fibrils nor in ordinary muscle have I ever 

 seen any sign of the transference of anisotropous substance from the 

 line of Hensen to the membrane of Krause, such as was originally de- 

 scribed by Merkel: a description which has been followed by many 

 subsequent writers. 



3) BüTSCHiii has , perhaps , recognized the same appearances but 

 has regarded them merely as a variety of "foam-structure". 



