On the structure of cross-striated muscle. 187 



as the planes above and below it 1 ). Nevertheless, the consideration 

 of the transverse section (Fig. 2) renders it at once evident that the 

 middle planes must have an entirely different appearance from those 

 above and below, and, in fact, this is so in all fibres of this kind, 

 i. e., with a radial arrangement of the muscle-columns, as can readily 

 be seen, not only in the acid preparation, but also in the fresh tissue 

 (see Fig. 5 A, B, C). In fact, at the middle plane the longitudinal 

 lines can no longer be distinguished and the place of their enlarge- 

 ments is taken by transverse lines, double when the rows of dots of 

 other planes are double, single when these rows are blended into one. 

 In fibres having the other kind of transverse section before referred 

 to, i. e., with a polygonal meshed network (e. g. Fig. 15) the dots 

 appear laterally united on slightly altering the focus up or down: this 

 again can be easily understood from a consideration of the transverse 

 section. 



If muscle which has been treated with acid be placed in chloride 

 of gold and the latter subsequently reduced by formic acid (ordinary 

 gold method) the longitudinal lines with their apparent enlargements 

 and also the transverse lines which unite these enlargements are 

 coloured by the reagent, the substance between the lines remains 

 colourless. The appearance produced is that of a violet reticulum 

 pervading a colourless matrix. 



I do not think that the statements hitherto made are subjects of 

 controversy. Except, perhaps, in one or two minor points of detail, 

 they are admitted by all. Rollett, it is true, has described the dupli- 

 cate enlargements which are seen as dark dots on the longitudinal 

 lines of the living fibre as being only observed at a high focus, and 

 he states that when the microscope is focussed downwards both these 

 dots and the longitudinal lines become clear, and a line of single dark 

 dots alternating with them becomes visible in the middle of the bright 

 stripe, This difference of appearance at high and low focus, I had 

 myself previously remarked and described 2 ), but I had been led to 



v ) Compare Rollett, Fig. lib, in Wiener Denkschriften, Bd. 51; and Melland 

 loc. cit. Fig. 1. 



-) Quain's Anatomy. 9th Edition, p. 123. 



