BLOOD AND NERVE SUPPLY 63 



observations suggest that cardiac muscle belongs to the group of tissues 

 possessing a syncytium. However, the section of cardiac tissue may very 

 possibly cut many cells without enclosing a nucleus. The continuity of 

 fibrils is an important observation from the physiological point of view; see 

 Circulation chapter. 



In certain parts of the heart, the cardiac tissue is not completely differ- 

 entiated and retains in the adult somewhat embryonic characters; for ex- 

 ample, the bundle of His running in the septum from the auricles to the 

 ventricles and the cells containing Purkinje's fibers lying immediately under 

 the endocardium. 



FIG. 79. 



FIG. 80. 



FIG. 79. Muscular Fiber Cells from the Heart. (E. A. Schafer.) 



FIG. 80. From a Preparation of the Nerve Termination in the Muscular Fibers of a 



Snake, a, End-plate seen only broad-surfaced; 6, end-plate seen as narrow surface. 



(Lingard and Klein.) 



Blood and Nerve Supply. The muscles are freely supplied with blood 

 vessels; the capillaries form a network with oblong meshes around the fibers. 

 Nerves also are supplied freely to muscles; the striated voluntary muscles 

 receiving them from the cerebro- spinal nerves, and the cardiac muscle from 

 both the cerebro-spinal and the sympathetic nerves. 



In striped muscle the nerves end in motor end-plates. The nerve fibers 

 are medullated; and when a branch passes to a muscle fiber, its primitive 

 sheath becomes continuous with the sarcolemma, and the axis-cylinder 

 forms a network of its fibrils on the surface of the muscle fiber. This net- 

 work lies embedded in a flattened granular mass containing nuclei of several 

 kinds; this is the motor end-plate, figures 80 and 81. There is considerable 

 variation in the exact form of the nerve end-plate in the muscle. In batrachia 

 the nerve fiber ends in a brush of branching nerve fibrils which are accom- 

 panied here and there by attached oval nuclei. 



