NER VE- TISS UE. Ill 



other cases, that the axis cylinders break up into their 

 constituent primitive fibrils before entering the cells. 

 2. In the PeripJiery. The peripheral termination 

 of nerves is a subject which presents extreme diffi- 

 culties to the histologist, and with few exceptions 

 the exact way in which this occurs is unknown. The 

 motor nerves, which are distributed in the voluntary 

 striated muscles, terminate in distinct, nucleated, 

 finely granular structures on the surface of the 

 fibres, called end plates ; those which go to the 

 smooth muscle tissue break up into fine plexures, 

 from which fibrils seem to pass either to the individ- 

 ual muscle-cells or to the surface of cell-bundles. In 

 the case of some of the nerves of special sense, we 

 have elaborate nerve-structures such as the retina, 

 auditory apparatus, etc. Again, we find the nerves 

 ending in small, complex, isolated bodies, such as the 

 so-called tactile corpuscles, etc. In some cases as 

 the nerves approach their peripheral terminations, 

 they lose the medullary sheath and neurilemma, and 

 the axis cylinder breaks up into very numerous, 

 exceedingly delicate fibrils which sometimes form 

 intricate plexuses; some of the fibrils appear to 

 terminate by free extremities ; others, it is probable, 

 end in single cells of various kinds ; but the whole 

 subject of peripheral nerve-endings is far too intri- 

 cate and too little understood, to demand more than 

 a passing mention in a course of study as elemen- 

 tary as that which now engages us. 



