STKUCTUKE OF STEIATED MUSCLE. 



77 



88, B). At either end of the sarcous element is a clear interval separat- 

 ing it from the membrane of Krause : this clear interval is more evident 

 the more the sarcostyle is extended, but diminishes to complete dis- 

 appearance in the contracted muscle (figs. 87, 88, A). The cause of this 



FIG. 87. FIBRES OF THE WING- 

 MUSCLES OP AN INSECT. 

 (Ranvier. ) 



The fibres are in different conditions 

 of extension, from A least ex- 

 tended, to D most extended, e, e, 

 sarcous elements ; m, m, mem- 

 branes of Krause ; be, clear inter- 

 vals on either side of Krause's 

 membranes, which in the stretched 

 sarcostyles are occupied by fluid 

 which has passed out from the 

 pores of the sarcous elements ; h, 

 separation of the sarcous element 

 into two parts, a clear interval 

 being left between them. 





is to be found in the structure of the sarcous element. Each sarcous ele- 

 ment is pervaded with longitudinal canals or pores, which are open in 

 the direction of Krause's membranes, but closed at the middle of the 

 sarcous element. In the contracted or retracted muscle, the clear part of 



A' 



FIG. 88. SARCOSTYLES or THE WINO- 



MUSCLES OP A WASP, PREPARED IN 

 THE MANNER DESCRIBED IN LESSON 



xvi., SEC. 3. (Highly magnified.) 



A, A', sarcostyles showing degrees of 

 contraction. B, an extended sarco- 

 style, with its sarcous elements separ- 

 ated at the line of Hensen. C, three 

 sarcostyles moderately extended. The 

 structure of the sarcous elements, is 

 shown diagrammatically. 



the muscle-substance has passed into these pores, and therefore disappeared 

 from view, but swells up the sarcous element and shortens the sarcomere : 

 in the extended muscle, on the other hand, the clear part has passed out 

 from the pores of the sarcous element, and now lies between this and the 



