On the structure of cross-striated muscle. 209 



stance before described as passing through those intervals to join 

 Krause's membrane (see Diagram). These fine striae very probably 

 represent fine septa, rather than mere filaments but I have not 

 succeeded in determining this point. 



Lastly we may consider the question whether the wing-sarcostyles 

 possess a membrane or not. They are certainly bounded by a fine 

 line which is very distinct opposite the clear intervals, but which 

 might, if the clear intervals were formed of solid substance, represent 

 merely the outline of that substance. There is, however, no evidence 

 whatever that these clear intervals are solid, on the contrary, every- 

 thing points to their being occupied mainly by a semi-fluid material. For 



Diagram of a sarcomere: A, moderately ex- 

 tended; B, contracted. 



K. K, membranes of Krause; ff, stria of Henseu; SE." 

 S. E,, sarcous element. 



dislocation appearances like that shown in Fig. 34 may frequently be 

 seen, which seem to indicate that the sarcous elements are not bounded 

 by solid substance at either end. If this clear substance is fluid, the 

 outline seen must represent a membrane, and this membrane is conti- 

 nuous, as we have seen (Fig. 31), with the membranes of Krause. 

 To the external surface of the sarcous element it adheres very closely 

 (if indeed it is not in actual continuity with the sarcous substance), 

 as is shown by the fact that in muscle-columns which have been 

 stretched (in the manipulation of teasing) the circumference of the 

 sarcous element may be dragged in one direction so that the cylinders 

 appear as if cupped (Fig. 33). 



We may next consider the differences between the appearances 

 presented by the wing-columns in the fresh condition or when treated 

 with acid or by the ordinary acid-gold method, on the one hand, and 

 when fixed by alcohol and treated by Eollett's gold method on the 

 other hand; and endeavour to discover a clue to these differences of 

 appearance. For in most cases in the living muscle the strongly 

 marked sarcous element of the alcohol preparation is scarcely visible. 



Internationale Monatsschrift für Anat. u. Pliys. VIII. 14 



