Animal and Vegetable Fibre. 325 



and relaxation. That announcement of the spiral structure 

 of muscle has, of course, had its full share of the derision in 

 which the paper in question has been held. 



Embryonic states of the Muscular Fibril mistaken by observers 

 for the fully -formed Fibril. 



In their endeavours to reach the ultimate structure of the 

 muscular fibril, observers have actually gone too far, and 

 reached the elements of a later generation. They passed over 

 what really admits of examination — the mature fibril, and 

 arrived at what almost defies the microscope — the embryo ; 

 mistaking and delineating for the fibril itself, a row of quad- 

 rilateral particles, the mere elements thereof ; mistaking for 

 the chain, as it were, a row of half-formed links destined to 

 compose the chain. I cannot wonder that in a row of quad- 

 rilateral particles, no one could discern my twin spirals ! 

 These particles are known to be light and dark in alternate 

 order. They give origin to the twin spirals. And for this 

 purpose the dark particles undergo what observers have en- 

 tirely overlooked, — division and subdivision, changes which 

 I figured in Miiller's ArcJiiv for 1850,* as seen with a micro- 

 scope of Plossl. And I have lately confirmed the observa- 

 tion when examining muscle with one of Smith and Beck's 

 microscopes along with Professor Allen Thomson, to whom 

 I refer, as having seen and delineated the divisions and sub- 

 divisions in question. As the quadrilateral bodies divide 

 and subdivide, the resulting minute particles become so far 

 dislocated, that they slide into positions for producing by 

 their union the spiral form. 



come smooth flat threads, with only here and there a trace of the crenate edge 

 derived from their originally twin spiral structure ; though this twin spiral 

 structure is distinct enough at earlier periods even here. 

 * Taf. XVII., Fig. 29, e,f, d. 



