152 Journal of Comparative Neurology. 



most abundantly to the funiculi laterales in the Ilnd thoracic 

 segment. 



Figures 13, 10, 14, 15 and 16 show what is thought to be 

 the behavior of the axones arising in the nucleus dorsalis. 

 Figure 13 is a detail from Figure ii (Thoracic VIII). Figure 



10 is a similar detail from a section taken through thoracic IV. 

 Figure 14 represents the central region of a section passing 

 through the caudal portion of thoracic II. Figure 15 shows 

 one half of the same area of a section through thoracic II but 

 about I cm. cephalad to Figure 14. Figure 16 is an outline 

 drawing from a section taken between Figure 14 and Figure 15 

 and comprises a reconstruction of the region of the nucleus 

 dorsalis, representing an approximate summation of the behav- 

 ior of the axones entering (^A) and leaving (6 ) the nucleus dor- 

 salis (^V^.) as determined from a study of sections intervening 

 between those represented by Figures 14 and 15. 



Sections taken through the cephalic end of thoracic 



11 show the nucleus rapidly diminishing in size. It disappears 

 in thoracic I and, consequently, is^absent in cervical VIII and 

 cervical VI (Fig. 7). 



It is unfortunate that the segments caudad to thoracic VIII 

 were not available from which to determine the behavior of the 

 nucleus dorsalis to its caudal termination. 



A careful examination of the section through thoracic VIII 

 (Figs. II, 12 and 13) shows the nucleus dorsalis \_N.d. (Cc.)] 

 not so distinctly defined as at more cephalad levels, and that it 

 contains numerous transversely cut (longitudinal) axones in 

 addition to cell bodies peculiar to the nucleus dorsalis or 

 Clarke's column. In thoracic IV (Fig. 10), four segments or 

 about 24 cm. cephalad to the level of Figure 13, the nucleus 

 has become larger and very distinctly defined. Under the mi- 

 croscope this distinct definition is seen to be due to an increase 

 in the number of meduUated axones coursing longitudinally in 

 it, giving it the nature of a fasciculus rather than a nucleus. It 

 is even enclosed by a capsule of connective tissue. 



Examination of the sections caudad to thoracic II reveals 

 very few if any a.xones which can be confidently considered as 



