On the structure of cross-striated muscle. 199 



wing -muscles certainly lend no support to the idea, for there is here 

 no appearance whatever of fibrillation within the sarcoplasm: the only 

 formed elements that are visible in it (besides the nuclei) being pe- 

 culiar rounded or angular granules which are frequently set in rows 

 between the muscle -columns and which stain deeply with chloride of 

 gold. Nevertheless it might still be that although the essential struc- 

 ture of the wing -muscles and of the ordinary muscles is the same, 

 i. e., consisting of striated sarcostyles embedded in a sarcoplasm-matrix, 

 there might be an additional structure non-essential to contraction, 

 but in some way advantageous to the particular mode of action of 

 the tissue, developed within the ordinary muscles. The appearances 

 of acid- and ordinary gold-preparations might be interpreted in favour 

 of the existence of such a special reticulum imbedded in the sarco- 

 plasm, but they may also be equally easily interpreted in favour of 

 the view that the lines and dots of the apparent network are merely 

 thickenings of the ordinary sarcoplasm. 



The transverse netiuorks of the leg-muscles. 



There is, however an appearance, which I have sometimes 

 obtained, which is in favour of the view that the transverse 

 networks are different in their chemical nature from the rest of the 

 sarcoplasm. 



The appearance referred to is represented in Fig. 11 a and b in 

 a longitudinal view of a beetle's muscle, and in Figs. 16, 18, in a trans- 

 verse view, i. e., as seen on the surface of a disk. The preparation 

 in which these fibres occured, was made by the vinegar-gold-formic 

 method. A portion of the insect was first placed in vinegar for a 

 lew minutes, then transferred to chloride of gold (1%) f° r an hour, 

 and afterwards left exposed to the light in dilute formic acid (about 

 1 in 500) for 24 — 48 hours. In a tissue thus treated, the relative 

 extent to which its several portions have been submitted to the action 

 of the preKminary acid and of the chloride of gold is necessarily very 

 different at different depths. The superficial fibres are naturally acted 

 upon most completely and for the longest time: to the deeper parts 

 both the acid and the gold take longer to penetrate, and these are, 



