482 DAVENPORT HOOKER 
position of a growing area by means of which the length of the 
cord is increased. No such mass of cells is found in this stage 
in the posterior segment. 
The tip of the anterior stump of the cord presents another 
significant step in the regenerative processes. From the time 
of the initial rounding off of the cut surfaces during the first 
24 hours after operation, no change beyond the protrusion of 
developing neuraxes and a few supporting fibers has taken place 
on either end. In this stage, however, some of the cells at the 
end of the anterior stump are seen to have migrated along the 
numerous fibrous connections bridging the gap. These cells, 
which may be differentiated from those of the mesenchyme by 
their large, round, darkly staining nuclei, are certainly neuro- 
blasts. They appear to have no processes and are supported 
by and intermingled with the nerve and ependymal fibers. They 
are found only in that portion of the fibrous connection which 
contains the processes of the neural supporting cells. None 
have as yet migrated from the posterior stump. 
Somewhat dorsal to the bundles of fibers which have been 
discussed, lies a second series of nervous connections between the 
two ends of the cord. These consist of smaller bundles of neu- 
raxes and connective tissue fibers, of which the former arise 
from the lateral portions of the dorsal half of the cord. They 
are easily identifiable as nerve fibers by the neurofibrillae which 
they contain. They may be regarded as establishing connections 
between the giant cell areas of the spinal cord and are, therefore, 
probably sensory in nature. Posteriorly their origin is distinct 
from that of the motor fibers. Anteriorly they enter the mass 
of short ependymal fibers arising from the whole cut surface of 
the cord. 
The 4 day stage is marked, then, by the completion of the 
primary reunion of the stumps and by the beginning of those 
processes which will ultimately restore the form of the regenerated 
cord. 
Larvae 24 weeks after operation. In the week and a half which 
elapsed between the last stage described and the present one, 
the tadpoles increased in size until they measured 14 to 16 mm. 
