196 E - A - Schäfer, 



acid -preparations, either unstained or afterwards stained by safranin 

 (which colours the reticulum), there is no great difficulty, if a suffi- 

 ciently high power and delicate adjustment be used, in satisfying one- 

 self of the fact. This is particularly clear in such pieces of muscle 

 as those shown in Fig. 12, which are from muscles which have been 

 broken up alter slight staining with gold, followed by prolonged action 

 of formic acid. At the first glance and when only one plane of the 

 reticular looking structure is observed, as represented in the figures, 

 the fragment, and especially its outlying and partially separated ele- 

 ments, seems to furnish support to the reticulum -hypothesis. But on 

 focussing gradually the lines shift laterally into others above and 

 below 1 ), and they are therefore certainly planes and not mere filaments. 



2. By observing the longitudinal lines in minute portions of reti- 

 culum which are deeply stained by gold and from prolonged action 

 of formic acid are completely isolated. Under these circumstances, if 



the longitudinal lines are mere filaments, they can appear as lines 



i 

 only, however carefully they are observed, or however highly they 



are magnified. If, on the other hand, they are formed of interstitial 

 (inter-columnar) substance, they will sometimes show lamellar exten- 

 sions or have a certain raggedness of outline due to the rupture of 

 such extensions. This appearance of lamellar extensions can, in fact, 

 sometimes be observed in fragments of the leg-muscles of insects which 

 have been thus treated (Fig. 13 A and B), and the question is thus 

 again answered in disfavour of the reticulum theory. 



3. By observing the behaviour of the transverse networks which 

 are seen on the separated disks of gold- and acid-treated muscle, when 

 the focus is carefully changed. 



The general appearance of these disks is well known. They are 

 formed by a separation which may occur across the fibre at various 

 levels. Those which have been by far the most abundant in my pre- 

 parations have been produced by a separation exactly in the middle 

 of the bright striae, between the double rows of dots, and correspon- 

 ding precisely to the situation of the inter-segmental membrane (mem- 



') This cannot, of course, he shown iu the figures. 



