NERVE 



613 



supposed to preside over the production of heat, and there- 

 fore to assist in the regulation of the temperature of the 

 body, but of whose existence as distinct and specific nerve- 

 fibres with no other function there is not the slightest proof), 

 peripheral nerves may be classified as follows : 



fSmell. 

 i. Nerves of special sensation 



Uight 



'Tactile sensation (per- 

 haps including the 

 nerves of muscular 

 sense). 



Temperature. 

 Pain. 



Centripetal 



or afferent^ 



fibres 



J Taste. 

 | Hearing. 

 U 



2. Nerves of general sensation 



3.* Possibly nerves other than 

 those included under i 

 and 2, concerned in reflex 

 changes in 



i. Motor nerves for^ 



Calibre of small arteries 

 (pressor, depressor). 



Action of heart. 



Visceral movements. 



Respiratory move- 

 ments. 



Glandular secretion. 



Ordinary skeletal 

 muscles. 



fSkeletal muscles. 

 Visceral ,, 



[Vaso-constrictor. 

 Vascular 



\ Cardio - augmen- 



Centrifugal \ tor. 



or efferent J Erector muscles of hairs (pilo- 



nbres V motor fibres). 



fVisceral muscles. 



Inhibitory nerves forj fVaso-dilator. 



[Vascular \ Cardio - inhi- 

 Secretory nerves. [ bitory. 



* It is not known whether the afferent portion of a reflex arc is always 

 composed of fibres included in the first two categories, although 

 undoubtedly in some cases it is. 



