33 



neurones of this ref:'ion by tliei r- sif.e, for they are really 

 giants. Their size is exceeded only by the neurones of the 

 midbrain roof-nucleus described in Section VI, Subsection 2. 



As to sxtei-nal form, the tract-neurones have a wide range; 

 a representative individual is drawn in fi||.?, t.n. There are 

 fron, three to five dendrites, and their disposition controls 

 the shape of the cell-body to a very high degree. The den- 

 drites may be given off at opposite extremities of the cell, 

 in which case the outline of the cell-body is a iruch elonga- 

 ted one. The form is rounded or stellate -/vhen the dendrites 

 are spaced at equal intervals. A dendrite is always a massive 

 process, very wide at its base, tapering quite gradually, and 

 reaching far out into the surrounding nervous matter. It gives 

 origin to but fev? branches. 



The axone always arises from the body of the cell. It 

 runs for a short distance in the transverse plane and then 

 turns into a longitudinal bundle of fibres on the same side 

 of the oblongata, or even on the opposite side. 



The internal organisation of a tract neurons is shown in 

 Pig. 44. The cytoplasm is voluminous in quantity, investing 

 the nucleus witb a thick layer on every side. The outline of 

 the nucleus is regular, and in form may be circular or oval. 

 There are always a remarkally soiall number of coarse chroiiiatin 

 granules, the chromatic material being distributed in the 

 form of a delicate reticulum. Subsidiary nucleoli are rarely 

 present. 



