462 



NERVOUS SYSTEM 



longitudinal meshes surrounding the fasciculi of fibres ; but they rarely 

 penetrate the sheath of Henle and usually do not come in contact with 

 the ultimate nervous elements. The veins are rather more voluminous 

 and follow the arrangement of the arteries. Lymph-spaces, lined with 

 delicate endothelium, are found in the connective-tissue sheaths of the 

 bundles of fibres. 



Branching and Course of the Nerves. The nerve-fibres in the 

 course of the nerves have no connection with each other by branching 



or inosculation. A bundle of 

 fibres frequently sends branches 

 to other nerves and receives 

 branches in the same way ; but 

 this is simply the passage of 

 fibres from one sheath to an- 

 other, the fibres themselves 

 maintaining throughout their 

 course their individual physio- 

 logical properties. The nerve- 

 fibres do not branch or inosculate 

 except near their terminations. 

 When there is branching of 

 medullated fibres, it is always 

 at the site of one of the nodes 

 of Ranvier. 



Termination of Nerves in 

 Voluntary Muscles. In man and in the warm-blooded animals generally, 

 the medullated nerve-fibres divide dichotomously near their endings in 

 the muscular fibres, the divisions taking place at the nodes of Ranvier. 

 The fibres finally resulting from these divisions pass to the sarcolemma 

 and terminate in a rather prominent mass called an end-plate, with six 

 to twelve or sometimes sixteen nuclei that are distinct from the nuclei 

 of the muscular fibre. The tubular membrane of the nerve-fibre here 

 fuses with the sarcolemma and the medullary substance is lost. By 

 the action of gold chloride, it has been shown that fibrils arise from 

 the under surface of the end-plates, which pass into the substance of the 

 muscular fibres, between the muscular fibrillae. These fibrils proba- 

 bly are connected with the axis-cylinders, but their exact mode of 

 termination in the muscular substance has not been satisfactorily 

 demonstrated. 



Although the sensibility of the muscles is slight as compared with 

 that of the skin and mucous membranes, they are not insensible and 

 they possess nerve-fibres other than those exclusively motor. Through- 



Fig. 100. Branching of a nerve in an abdominal 

 muscle of a mouse, x 120 (Sobotta). 



m, muscular fibres ; me, motor end-plates ; , nerve. 



