126 Journal OF Comparative Neurology. 



3. Two well defined longitudinal fasciculi occur within the 

 commissura grisea, one on either side of the mid line. 



4. These fasciculi probably disappear, as such, in the 

 XVIIIth or XlXth thoracic segment. 



5. At the level of the decussatio pyramidum these fasci- 

 culi are seen to arise from the decussating pyramidal axones 

 and may therefore be \.e:rm.ed fasciculi cerebro-spinales intemi. 



6. The nucleus dorsalis (Clarke's column), in addition 

 to the cell-bodies of neurones proper to it, contains numerous 

 longitudinally coursing meduUated axones giving it the appear- 

 ance of a fasciculus rather than a "nucleus." 



7. These longitudinal axones of the nucleus dorsalis in- 

 crease in abundance in passing from the Vlllth to the Ilnd 

 thoracic segments, and the cell bodies proper to the nucleus 

 seemingly do the same. 



8. These axones accumulate in the nucleus dorsalis 

 toward the Ilnd thoracic segment where they leave the confines 

 of the nucleus, passing obliquely cephalad across the cervix of 

 the columna posterior and enter the funiculi laterales probably 

 to form a fasciculus cerebello-spinalis (direct cerebellar tract). 



9. With the departure of these axones the nucleus dor- 

 salis becomes smaller and finally disappears in the 1st thoracic 

 segment. 



10. Afferent axones (from radix posterior) enter the con- 

 fines of the nucleus dorsalis more abundantly in the Ilnd tho- 

 racic segment than in the IVth or Vlllth and probably more 

 abundantly than in any segment caudad to the Ilnd thoracic. 



11. A constant and consistent grouping of the cell-bodies 

 of the columna anterior can not be claimed for the intumescen- 

 tia cervicalis 



IV. Comparative Studies. 



1. Scope and procedure. 



2. Table III, containing the transverse dimensions of the 

 intumescentiae cervicales and the average mean diameters of 

 the cell-bodies of the columnae anteriores from a series of twelve 

 mammals of diminishing body weights. 



3. The diameters of the medulla spinalis decrease grad- 



