THE STRUCTURE OF THE ELEMENTARY TISSUES. 



89 



ence with these the fibres appear under certain conditions subdivided 

 into oblong portions or " cells," the offsets from which are the means by 

 which the fibres branch and anastomose one with another. 



It should be noted, however, that the heart muscular fibres are not 

 the only ones which branch, since the fibres of the tongue of the frog, 

 especially where they are attached to the mucous membrane, present 

 this peculiarity; branching muscular fibres have also been noted in the 

 tongue, and in the facial muscles of other animals. And again, in the 

 animals in which two kinds of skeletal muscles occur, red and pale, in 

 the red muscles the fibres are much less distinctly striated transversely, 

 whereas their longitudinal striation is .more marked than in the pale 

 variety. They are also finer than other skeletal muscles. It should also 



Fig. 92. 



Fig. 93. 



Fig. 92. Muscular fibre cells from the heart. (E. A. Schafer.) 



Fig. 93. From a preparation of the nerve-termination in the muscular fibres of a snake, a, 

 End plate seen only broad surfaced, b, End plate seen as narrow surface. (Lingard and Klein.) 



be added that in these red muscles the sarcoplasm is much developed, 

 and the muscle nuclei are very numerous, and may be situated in the 

 middle of the fibre, as is the case with heart muscle fibres. 



Blood and Nerve Supply. The voluntary muscles are freely sup- 

 plied with blood-vessels; the capillaries form a network with oblong 

 meshes around the fibres on the outside of the sarcolemma. No vessels 

 penetrate the sarcolemma to enter the interior of the fibre. Nerves also 

 are supplied freely to muscles; the voluntary muscles receiving them 

 from the cerebro-spinal system, and the unstriped muscles from the 

 sympathetic or ganglionic system. 



The nerves terminate in the muscular fibre in the following ways: 

 (1.) In unstriped muscle, the nerves first of all form a plexus, called 

 the ground plexus (Arnold), corresponding to each group of muscle 

 bundles; the plexus is made by the anastomosis of the primitive fibrils 

 of the axis-cylinders. From the ground plexus, branches pass off, and 



