TERMINATIONS OF THE MOTOR NERVES. 



511 



The greatest part of the fibrous sheath of the nerves is composed of bun- 

 dles of white inelastic tissue, interlacing in every direction ; but it contains 

 also many elastic fibres, adipose tissue, a net- work of arteries and veins, and 

 " nervi nervorum," which are to these structures what the vasa vasorum are 

 to the blood-vessels. The adipose tissue is constant, being found even in ex- 

 tremely emaciated persons (Sappey). 



The vascular supply to most of the nerves is rather scanty. The arteries 

 break up into a plexus of very fine capillaries, arranged in oblong, longi- 

 tudinal meshes surrounding the fasciculi of fibres ; but they rarely penetrate 

 the sheath of Henle, and they do not usually come in contact with the ulti- 

 mate nervous elements. The veins are rather more voluminous and follow 

 the arrangement of the arteries. Lymph-spaces, lined by delicate endothe- 

 lium, are found in the connective-tissue sheaths of the bundles of fibres. 



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

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

 osculation. 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 another, the ultimate fibres themselves maintaining 

 throughout their course their individual physiological properties. The 

 nerve-fibres do n9t branch or inosculate except near their termination. When 

 there is branching of medullated fibres, it is always at the site of one of the 

 nodes of Ranvier. The branching 

 and inosculation of the ultimate 

 nerve-fibres will be fully described 

 in connection with their final dis- 

 tribution to muscles and sensitive 

 parts. 



Termination of Nerves in Vol- 

 untary Muscles. The mode of L. 

 termination of motor nerves in 

 voluntary muscles was indicated 

 by Doyere, in 1840, was quite fully 

 described by Rouget, in 1862, and 

 has since been studied by anato- FlG 

 mists, who have extended and 

 elaborated these researches. It is 

 the general opinion that but one 

 nerve-ending exists in each mus- 



175. Mode of termination of the motor nervzs 



(Rouget). 



A, primitive fasciculus of the thyro-hyoid muscle of the 

 human subject, and its nerve-tube: 1, 1, primitive 

 muscular fasciculus ; 2, nerve-tube ; 3, medullary 

 substance of the tube, which is seen extending to the 

 terminal plate, where it disappears ; 4, terminal 

 plate situated beneath the sarcolemma, that is to 

 say, between it and the elementary fibrillse ; 5, 5, 

 , ,,, , sarcolemma. 



CUlar nbre in the mammalia, While B, primitive fasciculus of the intercostal muscle of the 



lizard, in which a nerve-tube terminates : 1. 1. sheath 

 of the nerve-tube ; 2, nucleus of the sheath ; 3, 3, 

 sarcolemma becoming continuous with the sheath ; 

 4, medullary substance of the nerve-tube, ceasing 

 abruptly at the site of the terminal plate; 5, 5, ter- 

 minal plate ; 6, 6, nuclei of the plate ; 7, 7, granular 

 substance which forms the principal element of the 

 terminal plate and which is continuous with the axis- 

 cylinder ; 8, 8, undulations of the sarcolemma re- 

 producing those of the fibril la- ; 9, 9, nuclei of the 

 sarcolemma. 



several exist in cold-blooded ani- 

 mals. In man and in the warm- 

 blooded animals generally, the 

 medullated nerve - fibres divide 

 dichotomously near their endings 

 in the muscular fibres, each divis- 

 ion always taking place at a node of Ranvier. 



The fibres finally resulting 



