02 NORMAL HISTOLOGY. 



These tendon-spindles appear as sharply-defined, greatly-elon- 

 gated, elliptical masses (in the rabbit .25-. 75 mm. long and .O2-.oi 

 mm. broad), one end of which extends upon the tendon, while the 

 muscular pole is usually, although not always, continuous with the 

 adjoining muscle-fibres. The tendon-spindle is composed of a 

 distinct connective-tissue capsule, which, embracing two or more of 

 the primary bundles of the tendon, becomes united with the sheath 

 of the latter ; the inner surface of the spindle is covered with endo- 

 thelial plates. Medullated nerve-fibres to the number of two, three, 

 or four join the organ near its widest part, sometimes, however, at 

 one end ; after repeated division as medullated fibres, the nerves 

 spread out on the surface of the tendon as pale non-medullated 

 fibres, whose axis-cylinders unite to form a richly but irregularly 

 meshed arborescent figure ; the ultimate fibrillae, in addition to the 

 net-work, present numerous knobbed free ends. 



Blood-Vessels. The blood-vessels are accompanied by nerve- 

 fibres derived from the sympathetic system ; in addition to the pale 

 fibres, a few medullated ones usually take part in the production of 



the irregular net-work surrounding 

 FIG. 113. the larger vessels. From this plexus 



fine branches are given off, which 

 ultimately end between the muscu- 

 lar bundles of the media and within 

 the fibro-elastic tissue of the adven- 

 titia. The capillaries are accom- 



Nerve-fibres accompanying a small artery named and partly Surrounded by 

 (v), from ihe mesentery of rabbit ; gold prep- r . 



aration. delicate non-medullated nerve- 



fibres. 



The muscular tunics of the large lymphatic trunks are supplied 

 with nerves in a manner similar to the blood-vessels ; the delicate, 

 thin-walled lymphatics are probably without nerves. 



Glands. A detailed account of the nervous supply of the larger 

 glands will be given in connection with the consideration of the 

 several organs ; it may be mentioned here, in general, that the more 

 important glands are provided, in addition to the medullated nerves 

 often found passing through the substance of the gland in their course 

 to the contiguous skin or mucous membrane, with nervous bundles 

 in which non-medullated fibres predominate, but in which some 

 medullated ones also occur. These bundles form an interlobular 

 plexus, rich in ganglion-cells, which accompanies the larger excretory 

 ducts and blood-vessels, and gives off a few branches to be distributed 

 to the muscular coats of these tubes. Thin bundles of pale fibres 

 bear the smaller ducts company as far as the primary groups of acini, 

 and there break up into minute bundles of free axis-cylinders passing 



