37 

 linear masses. A small axone-hil lock of finely Granular inatter 

 lies just witl.in the orit^in of ttie axone. The tit^U-oid -bodies 

 near it are snialler and more irret^'.ular than elsewhere. 



The commissural neurones, in contrast with the tract- 

 neurones, always resj^ond to the stains applied; this indicates 

 a uniformly active physiological condition. Commissural neu- 

 rones doubtless have a not unimportant place in the economy of 

 this region of the brain, into which so many iaipulses sweep 

 through afferent nerve-fibres to great vital centres. The 

 chaining together of the opposite halves is precisely what we 

 should expect to find under such conditions, and the mechanism 

 is provided by the comi/iissural neurones Just described. 



4. iobus Vagi and Faseiovlus Communis . 



The Iobus vagi is the terminal station for the communis 

 fibres, components of the VII, IX, and X nerves. Its general 

 morphology has been outlined in Subsection 1. 



The structure of the Iobus vagi embraces a narrow 2one 

 next to the limitsns interna occupied chiefly by nerve-fibres; 

 and a deeper part in which there are both neurones and termi- 

 nating fibres. The course of the nerve-fibres will be consid- 

 ered later. 



a. neurones of the Lcbuf> Vagi. — The constituent neurones 

 of the Iobus vagi are many in number and closely crowded. They 



