CENTEAL ORGAN AND PEEIPHEEAL NEEYES (PHYSIOLOGICAL). 41 



lungs or the wall of a blood-vessel, one always finds delicate nerve-arbor- 

 izations in unsuspected numbers. A large portion of them end probably 

 in the peripherally placed sensory end-cells belonging to the reflex-arc of 

 the sympathetic; another portion may very probably be traced to the spinal 

 ganglia and even to the spinal cord itself. Especially the investigations of 

 the last few years, making use of the silver and methyl-blue stains, have 

 not only disclosed the wealth of nerves in the difEerent organs, but have also 

 shown that we have regarded the sensory innervation of the sensitive sur- 

 faces, as the skin and the gustatory mucous membrane, as much less fully 



Fig. 16. — a. Sensory epithelium of the nose sending the neuraxon as fila 

 olfactoria, or olfactory nerve, backward into the brain, where it breaks up into 

 branches. The neuraxon is, in this situation, a, non-medullated axis-cylinder. 

 The dendrite is represented by the distal process of the specialized olfactory cell. 

 6, Cell from the Ganglion spirale of the cochlea; the dendrite passes from its 

 peripheral arborization around the bristled cells of the macula, or hair-cells of 

 the organ of Corti direct to the ganglion-cell, whence the neuraxon passes as 

 Eamus eochlearis Nervi acustici toward the brain. (After Eetzius.) 



supplied than they really are. One finds there enormous plexuses of nerve- 

 fibers beneath and between the epithelial cells, and they send one, often 

 many, fine fibrils to each cell. Fig. 17 indicates, for example, how surround- 

 ing every hair there lies a veritable crown of nerve-fibrils {A and B), how 



