28 



THE SPINAL CORD. 



In this situation they pass up the cord, diminishing in number, at first rapidly and 

 afterwards more slowly, until at length a relatively small tract of degeneration is 

 found, occupying the postero-mesial angle of Goll's tract, in which it runs to the 

 nucleus gracilis (fig. 21, e). 



(J.) Section of the posterior roots of the dorsal and cervical nerves. After section 

 of one or more of these roots degeneration occurs immediately above the section in 

 the part of the postero-lateral column which is next to the posterior horn (figs. 22, 

 23, a). Somewhat higher up this becomes separated from the horn by other uncut (and 

 therefore undegenerated) nerve-root-fibres, and approaches the postero-mesial column. 

 Still higher it is found to have reached that column, where it is represented by a smaller 



Fig. 21. DIAGRAM SHOWING THE LEGENERATIONS IN THE POSTERIOR COLUMN WHICH RESULT FROM 



SECTION OF THE POSTERIOR ROOTS OF THE SECOND SACRAL TO THE SIXTH LUMBAR NERVES OF THE 



DOG. (Singer. ) 



a, section at the level of the sixth lumbar ; b, at the fourth lumbar ; c, from the middle of the 

 thoracic region. 



Fig. 22. DIAGRAM OF DEGENERATIONS FOLLOWING SECTION OF THE ELEVENTH AND TWELFTH THORACIC 



POSTERIOR NERVE-ROOTS OF THE DOG. (Singer.) 



a, section at the level of the twelfth thoracic ; b, at the third thoracic ; c. at the middle of the 

 cervical region. 



Fig. 23. DIAGRAM OF THE DEGENERATIONS FOLLOWING BILATERAL SECTION OF THE SECOND THORACIC TO 



THE FIFTH CERVICAL POSTERIOR NERVE-ROOTS OF THE DOG. (Kahler. ) 



, at the level of the first thoracic ; b, at the sixth cervical ; c, at the first cervical. 

 (Figs. 21, 22, and 23 are copied from Toldt's " Gewebelehre.") 



tract of degeneration, which in section lies obliquely across the column. With 

 regard to this degeneration in the postero-mesial column it is to be noted that while 

 that which results from section of the lower (lumbo- sacral) roots occupies in the 

 higher parts of the cord the postero-median angle, as above described, the degene- 

 ration resulting from section of dorsal roots lies next to this, that resulting from 

 section of lower cervical roots passes up Goll's column in its lateral part next 

 to the column of Burdach, and finally that resulting from section of upper cervical 

 roots is confined to Burdach's column, and ends in the nucleus cuneatus of the 

 medulla oblongata. In other words, the lower the root the more mesial is the 

 resulting long degeneration in the higher parts of the cord and in the medulla 

 oblongata. The fibres, as they enter the cord with the posterior nerve-roots, form 



