84 



HISTOLOGY 



found more or less granular brown pigment. This pigim-nt 

 increases with age (Fig. ">1 ). 



The cell substance shows darkly stained columns, which run 

 parallel to the long axis of the cell, and are separated by 

 unstained substance. These columns are commonly spoken of 

 as fibril bundles, and correspond with what v. Kolliker has 

 called " Muskelsaulchen." The unstained substance is generally 

 known as sarcoplasm. 



Careful observation and certain special methods of staining 

 reveal a definite relation between these two parts of the cell 

 (J. B. MacCallum). The fibril bundles are striated like those of 



Connect i re, .1 *_ 



tissue cell 



Radially arr>i<i<'<l s -* 

 fibril bundle*" Vjjjfp' 





 Pigment granules rf- jj*-~r* 



j 



''40- t 



~-S&&Z 



_____ ______ ___ 



From a cross-section through human heart muscle. X 800 



voluntary muscle, showing alternating light and dark bands. 

 In the centre of the light band is a narrow deeply staining 

 striation, known as Krause's membrane (Zwischenscheibe of 

 German writers). The broader dark band is called Brucke* 

 line, of doubly refractive substance (Querscheibe). In thin 

 sections, especially those stained by Kolossow's method, the 

 Krause's membranes are seen to belong to the sarcoplasm as 

 well as to the fibril bundles. This is shown in Fig. 52. The 

 sarcoplasm is divided into distinct disks by membranes, which 

 horizontally are continuous with the Krause's membranes of 

 the fibril bundles. There may be more than one of these disks 

 between two adjacent fibril bundles (Fig. 52, A), and at the 



