78 



GENERAL ANATOMY. 



epithelium of the skin of man and animals, especially in those parts of the skin 

 devoid of hair. They consist of a capsule composed of a very delicate, nucleated 



membrane, and contain two or more granular, 

 somewhat flattened cells, between which the med- 

 ullated nerve-fibre, which enters the capsule by 

 piercing its investing membrane, is supposed to 

 terminate. 



The nerves supplying tendons have peculiar 

 nerve-endings, and are especially numerous near 

 the point where the tendon becomes muscular. 

 In this situation spindle-shaped bodies are found, 

 and are known as the organs of Grolyi. They are 

 apparently composed of several tendinous bundles 

 fused into one, into which one or more nerve-fibres 

 pass, and, dividing, spread out between the tendon- 

 bundles. Nerve-fibres occasionally terminate in 

 tendons as end-bulbs or as small Pacinian cor- 

 puscles. 



In the organs of special sense the nerves seem 

 to terminate in cells, which are modified epithe- 

 lial cells, and have received the name of sensory 

 or nerve-epithelium cells. In reality, however, the 

 nerve-fibre is in these cases a process of the epi- 

 thelial cell, and if followed centrally will be found 

 to end by branching around a ganglion-cell. From 

 -this an axis-cylinder continues the path along 

 which the stimulus travels toward the brain. 

 These nerve-epithelium cells are to be regarded as 



FIG. 54. Pacinian corpuscle, with its n j-n j 



system of capsules and central cavity. Specially modified neurons. 



Motor TIPTVP<? arp rn VIP tv-ipprl pitlipr into nn- 

 motor nerves dl< 



striped or striped muscular fibres. In the un- 



. x r 



striped or involuntary muscles the nerves are de- 



j <? ,1 ,1 , j i 



rived from the sympathetic, and are composed 



maJnlv of tViP nrm mprlnllatprl fihrp<s Npar tlipiv 



maimy oi tne non-mec i nores. iMeartnen 



termination they divide into a number of branches, 

 which communicate and form an intimate plexus. 

 At the junction of the branches groups of ganglion-cells are situated. From 

 these plexuses minute branches are given off, which divide and break up into the 

 ultimate fibrillseof which the nerve is composed. These fibrillae course between 

 the involuntary muscle-cells, and, according to Elischer, terminate on the surface 

 of the cell, opposite the nucleus, in a minute swelling. Arnold and Franken- 

 hauser believed that these ultimate fibrillre penetrated the muscular cell and ended 

 in the nucleus. More recent observation has, however, tended to disprove this. 



In the striped or voluntary muscle, the nerves supplying the muscular fibres 

 are derived from the cerebro-spinal nerves, and are composed mainly of medullated 

 fibres. The nerve, after entering the sheath of the muscle, breaks up into fibres, 

 or bundles of fibres, which form plexuses, and gradually divide until, as a rule, 

 a single nerve-fibre enters a single muscular fibre. Sometimes, however, if 

 the muscular fibre is long, more than one nerve-fibre enters it. Within the 

 muscular fibre the nerve terminates in a special expansion, called by Kiihne, who 

 first accurately described them, motorial end-plates (Fig. 55). * The nerve-fibre, 

 on approaching the muscular fibre, suddenly loses its white matter of Schwann, 

 which abruptly terminates ; the neurilemma becomes continuous with the sarco- 

 lemma of the muscle, and only the axis-cylinder enters the muscular fibre, where 

 it immediately spreads out, ramifying like the roots of a tree, immediately beneath 



1 They had, however, previously been noticed, though not accurately described, by Doyere, who 

 named them " nerve-hillocks." 



. 



a. Arterial twig, ending in capillaries, 

 which form loops in some of the inter- 



capsuiar spaces, and one penetrates to 



the central capsule. 6. The fibrous tissue 



of the stalk prolonged from the perineu- 



rium. n. Nerve-tube advancing to the 



central capsule, there losing its white 



matter, and stretching along the axis to 



the opposite end, where it is fixed by a 

 tubercular enlargement. 



