1 82 Journal of Comparative Neurology. 



caudal end of Thoracic II. Shows beginning of the comparatively sudden de- 

 parture of axones from nucleus dorsalis. Nucleus on right of figure shows 

 axones leaving nucleus and crossing cervix of columna posterior to enter funi- 

 culi laterales. In nucleus on left this process has not yet begun. Shows ap- 

 pearance of nucleus in double contour as it occurs in this segment and in seg- 

 ment caudad to this. F. c. /., larger than in Fig. lo (Thoracic IV). X lo. 



Fig. 15. Photograph of one side of central region of section through 

 Thoracic II, about 1 cm. cephalad to Fig. 14. Showing the level at which the 

 departure of axones from the nucleus dorsalis is at its maximum. In leaving the 

 nucleus, axones pass obliquely cephalad and thus their entire course is not shown 

 in transverse section. F. c. «., nearly as large as in cervical VI (Fig. 7). Com- 

 missura alba anterior involves pia mater of fissura mediana anterior. X 10. 



Fig. lb. Slightly diagrammatic reconstruction giving summation of appear- 

 ances as seen in sections between those represented in Fig. 14 and Fig. 15. A, 

 afferent axones (from radix posterior and fa-ciculus cuneatus) coursing toward 

 and into nucleus dorsalis, Nd. D., small longitudinal fasciculi of afferent 

 axones (.4). C, axones from nucleus dorsalis crossing cervix columnae poste- 

 rioris to enter funiculi laterales, probably fasciculus cerebello-spinalis. 



PLATE XIII. 



The purpose of the twelve figures of this plate is to show the comparative 

 size and the shape in section of t.he large cell-bodies present in the columnae 

 anteriores in the thickest segment of the intumescentia cervicalis of the differ- 

 ent mammals named. They are arranged in the order of the normal body-weight 

 of the animals. Each figure represents one of the ten largest cell-bodies found 

 in three adjacent sections of the segment and which were measured to obtain 

 the average mean diameters recorded in column i of Table III. Under each 

 figure is given the actual diameters of the cell-body in terms of micra and the 

 name of the animal from which it was taken. The lines drawn through each 

 figure represent the diameters which were measured and also show the method 

 employed in judging the diameters which involved the larger dendrites. All 

 the figures are camera drawings made under a magnification of 712 diameters. 

 They are reduced to scale. Zeiss apparatus was used throughout for both the 

 measurements and the drawings. 



