STRUCTURE OF STEIATED MUSCLE. 



73 



rows of apparent granules are seen lying in or at the boundaries of the 

 light streaks, and very fine longitudinal lines may, with a good micro- 

 scope, be detected uniting the apparent granules (fig. 81). These fine 

 lines, with their enlarged extremities the granules,, are more conspicuous 

 in the muscles of insects. They indicate the divisions between the 

 longitudinal elements (muscle-columns, sarcostyles) which compose 

 the fibre, and in preparations treated with dilute acid they appear to 

 form part of a fine network, which pervades that substance, and serves 

 to unite the granules both transversely and longitudinally. This net- 

 work, which is sometimes very distinct in preparations of muscle 

 treated with chloride of gold, is, hoAvever, a network in appearance 



FIG. 80. SARCOLEMMA OP MAM- 

 MALIAN MUSCLE, HIGHLY MAG- 

 NIFIED. 



The fibre is represented at a place 

 where the muscular substance has 

 become ruptured and has shrunk 

 away, leaving the sarcolemma 

 (with a nucleus adhering to it) 

 clear. The fibre had been treated 

 with serum acidulated with acetic 

 acid. 



FIG. 81. MUSCULAR FIBRE OF A 

 MAMMAL EXAMINED FRESH IN 



SERUM, HIGHLY MAGNIFIED, 

 THE SURFACE OF THE FIBRE 

 BEING ACCURATELY FOCUSSED. 

 The nuclei are seen on the flat at the 

 surface of the fibre, and in profile 

 at the edges. 



only : in reality it is the optical expression of the interstitial substance 

 which lies between the muscle-columns. This substance is termed 

 sarcoplasm. 



A fine clear line is sometimes seen running transversely across the 

 fibre in the middle of each dark band. This is termed Hensen's line. 



On examining the transverse section of a fibre with a high power, it 

 is seen to be subdivided everywhere into small angular fields, the areas 

 of Cohnheim. These represent sections of the sarcostyles of which the 

 fibres are composed, and into which they may be split after death, or 

 after being hardened in certain reagents, e.g. chromic acid or osmic 

 acid. 



