CARDIAC MUSCULAR FIBRE. 



65 



stance in the living muscle is semi-fluid, but in hardened tissue it 

 can be split up, as indicated at 0, into rods, the sarcous elements. A 

 transparent line, D, in this contractile substance can sometimes be 

 demonstrated; it is known as Hensen's middle disc. 



Macerate human muscle, preferably that from the tongue, in dilute 

 chromic acid for twenty-four hours; wash, tease in water, cover and 

 focus H. Fig. 49 was drawn from such a preparation. 



The sarcolernma is best seen where the contractile substance has 

 been broken. The muscle nuclei are seen at various points beneath 

 the sarcolemma. Portions of a fibre have been split off transversely 

 in places, indicating the discs of Bowman. Sarcous elements are in- 

 dicated where the fibre has been split during the teasing. The 

 capillaries are arranged in a direction parallel to the fibres, with fre- 

 quent transverse connections. 



CARDIAC MUSCULAR FIBRE. 



It presents the following characteristics: 



1. The fibres are smaller than those of ordinary skeletal muscle, 



2. They are striated both transversely and longitudinally, 



3. They branch, forming frequent inosculations. 



FIG. 50. TEASED CARDIAC MUSCULAR FIBRE. 

 Stained with heema. X 400 and reduced. 



4. They are divided by distinct transverse lines into short prisms. 



5. Their nuclei are situated within the fibre. 



6. They present no distinct sarcolemma. 



5 



