58 PRINCIPLES OF PHYSIOLOGY 



on account of its striped appearance when 

 examined microscopically. It consists of a 

 mass of elongated nucleated cells, each an 

 inch or two in length, having pointed ends, and 

 its minute structure is so complicated that it 

 is still one of the puzzles of histologists. The 

 cell substance has become highly differentiated 

 into disk-like structures, which give the 

 tissue an appearance of striation, that is of 

 bands passing transversely across the fibre. 

 There is also a differentiation into longitudinal 

 structures called sarcostyles or fibrils, each of 

 which shows striation, due to the existence 

 of sarcous elements, or sarcomeres. When a 

 fibre contracts the sarcous elements contract 

 and a fluid substance, the sarcoplasm, is 

 pressed out in both directions till it is arrested 

 by a thin membrane, the membrane of Krause. 

 This membrane passes transversely across a 

 fibre and separates bundles of sarcostyles. 

 The sarcous elements are doubly refractive, 

 while the other parts between are singly 

 refractive. There appears also to be a very 

 fine reticulum, with longitudinal meshes, 

 n the fibre Another variety, called non- 



