246 



SPECIAL HISTOLOGY. 



In some cases, even, the gradual attenuation of the fibres may be 

 directly observed, proving that the diminution in size does not take 

 place, in this case at least, in consequence of division. Thus, in the 



Fig. 102. 



Fig. 103. 



omohyoid, I have noticed several nerve-fibres of 0-004-0-0053 of a line, 

 derived from trunks measuring 0-05 0-07 of a line, become attenuated 

 (within a distance of 0-15-0-2 of a line), to a diameter of 0-002-0-0026 

 of a line, and, after a further course of 0-.4-0-5 of a line, acquire that 

 of the smallest fibrils, or 0*001 of a line. Simultaneously with this 

 change in size, the nerve-fibres assumed in all respects the aspect of the 

 so-termed sympathetic nerves, and ultimately became pale, with a simple 

 contour line, and disposed to form varicosities ; at the same time that 

 they appeared to lose every vestige of a coat composed of connective 

 tissue, they still retained dark borders, and consequently were not non- 

 medullated fibres (or free axis-cylinders), such as are seen in other ter- 

 minations of nerves. 



Nervi vasorum (vascular nerves), accompanying the bundles of vessels, 

 oc*cur in all muscles, and, according to the size of the latter, form 

 larger or smaller branches. They are composed only of the smallest 

 fibres, and always follow the course of the large vessels, which can still 



FIG. 102. Ultimate expansion of the nerves in the omohyoid muscle of Man, magnified 

 350 diameters, and treated with soda: a, interstices of the terminal plexus; b, terminal 

 loops ; c, muscular fibres. 



FIG. 103. Divisions of the primitive nerve-fibres in muscle, magnified 350 diameters: 

 .>#, double division from the omohyoid muscle in Man ; a, neurilemma ; i>, division of a 

 nerve from a facial muscle of the Rabbit into three apparently pointed twigs. 



