208 E. A. Schäfer, 



band, lias been taken by most authors to represent the accessory dish 

 which was described by Flögel and by Engelmann in the leg'-muscles. 

 I shall have more to say regarding' this structure at the end of this 

 article, and the cause of the separation of the sarcous element into 

 a number of separate disks in the extended sarcostyle will also be 

 considered later in dealing with the eifects of extension and retraction 

 upon the cross-striation of muscle. 



In a preparation of the wing-muscle made in the manner above 

 described, viz: fixation by alcohol and subsequent staining by gold 

 and reduction in formic acid, a certain number of muscle-columns may 

 always be found, in which the formic acid has dissolved every part 

 except the sarcous elements, which then lie free in the preparation as 

 minute cylindrical disks, some of which are placed so as to be seen 

 in profile while others lie flat. By touching the cover-glass with 

 a needle the same sarcous element may be made to roll over and 

 may be observed from both points of view, or in any intermediate 

 position. These sarcous elements are usually somewhat swollen by 

 the acid. When they are viewed in profile, i. e. , in longitudinal 

 optical section, they show very distinctly the longitudinal streaking 

 which has already been mentioned (Fig. 37, B). When viewed on 

 the flat with a moderately high power the disks have a dotted appe- 

 arance, but when the highest powers of the microscope are employed 

 (. 2 mm homogeneous immersion apochromatic objective with No. 8 

 or No. 12 compensating eyepiece) the dots resolve themselves into 

 clear circular holes in the otherwise continuous substance of the sar- 

 cous element. These holes are seen over .the whole area of the disk, 

 and are visible so far as can be determined in every plane (Fig 37, A); 

 they therefore represent tubular canals. From this observation it may 

 be concluded that the cylindrical disks hitherto spoken of as sarcous 

 elements, are not composed of a bundle of similar but simpler elements 

 which can be described as rods, but are formed of a mass of chromatic 

 substance which is everywhere perforated by longitudinal tubules. These 

 tubules, which thus pervade the sarcous element, appear in the longi- 

 tudinal optical section of the sarcostyle to be continuous with or to 

 opeu into the clear intervals, between the fine striae of sarcous sub- 



