On the Minute Structure of Striped Muscle, Sfc. 



tractile tissue than from the highly evolved tissue of the striped 

 muscle.* 



EXPLANATION OF PHOTOGEAPHS. (PLATE 6.) 

 Photograph I. 



Photograph of the muscle of a Crab in a state of relaxation, and magnified 100U 

 diameters. Dobie's lines are seen as narrow dark bands running across the 

 fibres, and corresponding to tiny bulgiugs of the individual fibrils ; seen best 

 at the upper edge of the fibre. The clear stripes on either side of Dobie's lines 

 correspond with constrictions in the fibrils, and the dark stripes correspond 

 with broad swellings. The cement substance between the fibrils appears light 

 in colour. 



Photograph II. 



lotograph (700 amplifications) of a moist film of collodion, upon which a piece of 

 relaxed Crab's muscle had been pressed and had then been withdrawn. In this 

 " intaglio " all the appearances of the relaxed Crab's muscle are to be seen, 

 those parts which are ( dark in Photograph I coming out white in the intaglio. 

 The cement matter and the clear stripes are dark, and the dark stripes and 

 Dobie's lines come out light in colour. 



Photograph III. 



Photograph of a moist film of collodion, upon which a piece of contracted Crab'* 

 muscle had been pressed and had then been withdrawn. The striping is that 

 of the contracted fibre in all its detail ; the approximation of the cross-stripes 

 to each other and the absence of Dobie's line are points especially to be noted. 

 Owing to the collodion film varying in its thickness, the intaglio is photo- 

 graphed at different focal planes, and the dark stripe, which appears light in 

 the lower part of the photograph, comes oxit dark in colour at the upper part. 

 The edge of the intaglio is better seen than in Photograph II, and by the aid 

 of a lens one can readily see in the original negative the interfibrillar matter. 



I am much indebted to the Cambridge Engraving Company for 

 le excellent manner in which the photographs just described have 

 Ben reproduced. 



Professor P. G. Tait has recently suggested to me, that, owing to their 

 ricosity, the fibrils will be able, as it were, to get a better "grip" of the inter- 

 brillar matter, so that during contraction or relaxation the muscle will be able more 

 tually to move as a whole. 



