ARRANGEMENT OF THE NERVE FIBRES. 



213 



varies between 0.0133 and 0.0037 mm - It l' cs in the axis por- 

 tion of the papilla, and consists of homogeneous connective 

 substance, with transverse and obliquely disposed nuclei. 

 The whole thing acquires thereby a peculiar appearance, 

 which reminds one of a fir cone. The nerve fibres (with their 

 trunks passing from below upwards) arrive at our structure 

 singly, doubly, or three or four together. Their neurilemma 

 passes over into the capsule. They themselves, after previous 

 curved excursions or- looped windings, enter the tactile bodies 

 manifoldly. Having become pale and transformed into axis 

 cylinders, they soon disappear from the eye. 



We have thus become familiar with this most peculiar man- 

 ner of termination of the sensory nerves. 



How do the millions of other simple sensory nerve fila- 

 ments terminate ? We now raise this question. 



Unfortunately, we know but little concerning this at the 

 present time. Much has been stated concerning the terminal 

 plexuses of the finest nerve fibres, in the frog as well as in 

 mammals. 



It is, furthermore, settled that occasionally the terminal 

 filaments of the sensory nerves pass into the epithelium and 

 end in it. We have already become familiar above (p. 207) 

 with the most beautiful example of this kind, in the cornea of 

 the eye (Fig. 36). The primitive fibrillar here run out between 

 the epithelial cells. 



Others speak of a penetration of these filaments into the 

 cells, and of a termination in the nucleolus ; thus Hensen 

 concerning the skin of the frog, Lipmann concerning the 

 posterior corneal epithelium of the same animal. 



Other cutaneous nerves appear finally in the form of fine 

 non-medullated filaments, which terminate in small cells, 

 0.0088 to 0.0033 mni. in size, embedded in the human 

 rete Malpighii ; a portion of them may also pass further 

 downwards. They have been called Langerhans' corpus- 

 cles. 



Something similar has been subsequently observed in quite 

 different mucous membranes, where these Langerhans' struc- 



