CH. VI.] 



VOLUNTAKY MUSCLE 



81 



striated muscle, adhere very closely to the writings of Professor 

 Schafer. 



If the surface is carefully focussed rows of apparent granules are 

 seen lying at the boundaries of the light streaks, and fine longitudinal 

 lines passing through the dark streaks may be detected uniting the 

 apparent granules (fig. 104). 



In specimens treated with dilute acids or gold chloride, the 

 granules are seen to be connected side by side, or transversely also. 

 This reticulum (fig. 105), with its longitudinal and transverse meshes, 

 was at one time considered to be the essential contractile portion of 

 the muscular fibre ; it was thought that on contraction the transverse 

 networks, with their enlargements, the granules, became increased by 



FIG. 105. Portion of muscle-fibre of 

 water-beetle, showing network 

 very plainly. One of the trans- 

 verse networks is split off, and 

 some of the longitudinal bars are 

 shown broken off. (After Mel- 

 land.) 



Fio. 106. Transverse section through 

 muscular fibres of human tongue. 

 The nuclei are deeply stained, 

 situated at the inside of the sar- 

 colemma. Each muscle fibre 

 shows "Cohnheim's areas." 

 x 450. (Klein and Noble Smith.) 



the longitudinal strands diminishing in length and running into them. 

 Most histologists have rejected this idea, and regard the network as 

 mere interstitial substance lying between the essentially contractile 

 portions of the muscle. A muscular fibre is thus made up of what 

 are variously called fibrils, muscle-columns or sarcostyles ; and the 

 longitudinal interstitial substance with cross networks comprising 

 the reticulum just referred to is called sarcoplasm. By the use of 

 certain reagents, such as osmic acid or alcohol, the muscle-columns or 

 sarcostyles may be completely separated from one another. 



A transverse section of a muscular fibre (fig. 106) shows the 

 sections of these sarcostyles ; the interstitial sarcoplasm is represented 

 as white in the drawing. The angular fields separated by sarcoplasm 

 may still be called by their old name, areas of Cohnheim. 



Lf, instead of focussing the surface of a fibre, it is observed in its 



F 



