On the structure of cross-striated muscle. 181 



The chief diffìcili ty to this view is that presented by the structure of 

 the wing" muscles of insects, in which the so-called fibrils are very 

 obviously the contractile part. This difficulty is attempted to be got 

 over in various ways, viz: 1. by denying the fact that these fibrils 

 are contractile (Ramôn y Cajal); 2. by looking upon them as re- 

 presenting the longitudinal part of the assumed reticulum (van Ge- 

 buchten); 3. by regarding these muscles as a form of contractile 

 tissue sui generis, and not in any way comparable to the ordinary 

 tissue; and 4. by the simple plan of ignoring the difficulty altogether. 

 It will, however, I think appear that none of these expedients are of 

 any avail; for the essential correspondence in structure between the 

 two kinds of fibres cannot be overlooked when they are rigidly com- 

 pared with one another *). It is a well-known fact that, in many 

 insects, the wing muscles in place of being of the usual obviously 

 fibrillar type, approach near to or are even identical in structural 

 appearance with the ordinary muscles of the limbs 2 ). On the other 

 hand, in some insects, the leg-muscles have, even in the living con- 

 dition, so markedly fibrillated an appearance and so large an amount 

 of granular interstitial substance (vide the portion of muscle shown in 

 Fig. 3) as to approach the appearance of the ordinary wing-muscles, 

 and doubtless a full investigation would disclose a complete series 

 of transitions between the two. It is clear therefore that any essen- 

 tial structure that is possessed by the one kind of cross-striated 

 muscle must be found in the other kind; hence it follows that if the 

 network, which, in the opinion of most of the authors belonging to 

 camp B, is the truly contractile part of the ordinary muscles, is re- 

 presented by a non-contractile interstitial substance in the wing-muscles 

 while, on the other hand, the part of those muscles which corresponds 

 to the inter -reticular substance of the leg-muscles is demonstrably 

 contractile, the opinion in question necessarily falls to the ground. 



1 ) It is difficult to understand why Rollett (Wiener Denkschriften, Bd. 51. 

 S. 62) should regard the wing muscles as in no way comparable to the ordinary 

 muscles, since their structure affords a most complete confirmation to the view which 

 he has taken of the general structure of muscle. 



-) For the evidence of this, see Aubert, Zeitschr. f. wiss. Zool. 1853; quoted 

 and added to by Kölliker, Zeitschr. f. wiss. Zool. Bd. 47. 1888. pp. 690, 691. 



