CAKDIAC MUSCLE 



57 



most 



tion. The numerous branches of its cells constitute the 

 prominent histologic characteristic of the heart muscle. 



The nucleus of the cardiac muscle cell is oval in shape, and is 

 situated in its center. Like that of smooth muscle, its nuclear 



FIG. 59. CARDIAC MUSCLE OF THE HUMAN HEART; THE ABUNDANT BRANCHES ARE 



PLAINLY SHOWN. 

 Longitudinal section. Hematein and eosin. Photo, x 120. 



wall is distinct and its chromatin is distributed in coarse, widely 

 separated karyosomes. 



The cytoplasm can be differentiated into a clear sarcoplasm and 

 dim fibril bundles. The sarcoplasm is extremely translucent, which 

 accounts for its apparently lighter color, and occurs most abun- 

 dantly in the neighborhood of the nucleus. The fibrils, less trans- 

 lucent, and therefore darker in appearance than the sarcoplasm, 



