154 MUSCULAR SYSTEM. [sect. 84. 



plexuses consist only of very fine fibres. These, however, are 

 still dark-bordered, and of O'ooi'" to 0-0025'" in diameter; and, 

 in particular instances, the successive attenuation of individual 

 fibres can be directly observed, which proves that, at least in these 

 cases, it is not occasioned by division. 



Nervi Vasorum occur in all muscles, and, accompanying the vas- 

 cular bundles according to the size of the latter, form coarser or finer 

 branches. They contain only the finest nerve-fibres, and always 

 follow vessels of sufficient size to be recognised as arteries and 

 veins. I have never seen their termination, and only know this 

 much, that they are often wanting on the smallest veins and 

 arteries, and never occur on the capillaries. Here and there one 

 or more fibres of the muscular nerves are seen joining them, which 

 is in accordance with the fact that the nervi vasorum of many 

 parts (the limbs, for instance) may be shown to come from the 

 spinal nerves. The smaller tendons have no nerves ; the larger, 

 as the tendo Achillis and tendon of the quadriceps, the centrum 

 tendineum (Luschka) for the most part contain only nervi vasorum. 

 Fascial and tendinous sheaths are destitute of nerves, and also, so 

 far as I have hitherto seen, the synovial capsules of the muscular 

 system. 



According to my investigations, the distribution of the nerves in many of 

 the small-sized muscles in man, is very limited, so that whilst one part of 

 the muscle is, in its entire breath and thickness, unusually rich in nerves, 

 the rest is entirely, or almost entirely, destitute of them. In other muscles, 

 the nerves are distributed over larger portions, but appear also here to 

 come in contact with each" primitive fibre only at one 'very limited spot. 

 From this we may, with great probability of its truth, deduce the general 

 law, that the muscular fibres do not stand in connection with the nerves in 

 their entire length, but only at one small point ; whence the further deduc- 

 tion follows, that when we wish to electrify the muscles and cause them to 

 contract with energy (electrisation loealisee of Duchenne), that point is to be 

 chosen at which the nervous trunk enters it. Long muscles, as the latissi- 

 mus, sartorius, etc., may, perhaps, form an exception to this law, as in these, 

 perhaps, the fibres come in contact with the nerves at two or three points ; 

 but more accurate information is wanting as to the arrangement in these 

 cases. 



In many animals belonging to the invertebrata, free terminations of the 

 nervous fibres, and their attachment to the muscular fibres by expanded 

 extremities, are well known. In the vertebrata, Midler and Briicke first de- 

 scribed divisions of the nerve-fibres in the ocular muscles of the pike. In 

 the amphibia, divisions and free terminations have become well known, since 

 Wagner discovered them in the frog. The divisions are remarkably beautiful 

 and numerous. They commence, in the small trunks and branches, in nerve- 

 tubes 0-004'" to 0-006'" in diameter, and continue to divide, with gradual 



