88 ELEMENTARY PHYSIOLOGY. . [vill. 



tral spots. (This section should be preserved 

 for examination later, Less. xvi. A. 3.) 

 The reduction of nitrate of silver by the cement 

 substance between the muscle ceils will be seen 

 later, Less. xn. C. 4. 



12. Tease out thoroughly a small portion of cardiac 

 muscle preserved in potassium bichromate 1 . 

 Note that 



a. The striation is less distinct than in skeletal 

 muscle. 



I. No sarcolemma is present. 



c. At short intervals along the fibres are not 

 very distinct transverse bands of hyaline 

 cement substance, this joins together the 

 muscle cells of which the fibres are composed. 

 At about the centre of each muscle cell is 

 a nucleus. (The nuclei will become more 

 evident if the tissue be stained with alum- 

 hoematoxylin or picrocarmine.) 



d. The isolated muscle cells may frequently be 

 seen to have a short obliquely running pro- 

 cess ; in the fibres the processes of the cells 

 are joined to other similar processes by a 

 little cement substance, forming thus the 

 anastomoses of the fibres. 



1 Good preparations can also be obtained by the following method 

 (Ranvier). Thin sections in the direction of the fibres are cut from a 

 fresh heart, placed in chromic acid '02 p.c. for one day, then washed 

 well with water, placed in picrocarmine for one or more days, washed 

 and mounted in acid glycerine. 



