430 DAVENPORT HOOKER 
as are those found in the wound EF’, with the exception of the 
fact that the nerve fibers from the latter surface appear at a 
slightly later time than those from CD. This would be ex- 
pected from Coghill’s demenstration of the caudally progress- 
fas L 
a we Cae salle fe Dee * 
U 
ac eae Oe Ee D Piero 
JE 
Fig 3 Diagrams showing the nature of the nerve processes growing out 
from the cut ends of the spinal cord. The arrows point toward the head, except 
in the segment HD in III, where it points toward the cephalic end of the re- 
versed piece; am, ascending motor; as, ascending sensory; dm, descending motor; 
ds, descending sensory processes. 
I represents the condition found after a single severing cut through the spinal 
cord. From the caudal extremity of the cephalic stump, A, only descending 
motor processes arise. From the cephalic end of the caudal stump, B, both 
ascending motor and ascending sensory fibers are developing. 
II represents the condition in a spinal cord which has been completely sev- 
ered in two places. The wounds CD and EF each show the same conditions as 
the wound AB above. 
III represents the condition in the spinal cord of an embryo, the middle sec- 
tion of which, ED, has been reversed end-for-end. The stump / shows only 
descending motor processes arising from it, while the stump D has both sen- 
sory and motor fibers. A comparison of figures II and III shows that by the 
reversal of the position of the middle segment no change has been brought about 
in the nature of the processes which arise from the surfaces D and E. 
ing differentiation of the neurones of the cord. In both of these 
wounds the motor fibers from the cephalic surfaces are the first 
to appear, those arising from H making their appearance some- 
what later than those from C, but before the sensory fibers have 
begun to grow out from D. The motor fibers appear in the 
