188 JOURNAL OF COMPARATIVE NEUROLOGY. 
Spinal Cord of Mammals. 
It will perhaps be noticed that in this review the question 
of the restoration of function has been carefully avoided. This 
is because we are interested here only in the presence or ab- 
sence of new-formed nerve elements, and this is a matter which 
can be studied quite apart from the physiological value of these 
elements. This restriction will make possible a clearer view of 
the literature on the regeneration of the spinal cord of mam- 
mals, which has been much confused by the failure to appre- 
ciate the difference between reflex and voluntary movements. 
Eicuorst and Naunyn (10) (1874) crushed the spinal cord 
of dogs. In the connective tissue which developed in this 
region many nerve fibers were found. These resembled the 
fibers of peripheral nerves, from which Ercuorst believes they 
are ingrowths. In one instance he was able to follow one of 
these fibers to a spinal ganglion. Since it was impossible to 
prove that all the fibers had been destroyed by crushing, these 
results were not favorably received. To meet this objection 
Eicuorst (11) (1875) completely severed the spinal cord of 
several dogs and was able to confirm his previous results. The 
article published by Masius (23) in 1880 describes the removal 
of a part of the sacral cord in young dogs. Microscopic ex- 
amination, made after healing had occurred, showed in the 
connective tissue many nerve fibers, mostly myelinated and 
grouped in bundles. These were continuous with the fiber 
tracts of the stumps. No nerve cells were found in the scar 
tissue. A month anda half after complete transection of the 
cord, STROEBE (30) (1894) found in the scar nerve fibers which 
had grown in from the dorsal roots. These fibers never com- 
pletely crossed the line of the incision. He noticeda few 
mitotic figures in the ependyma cells lining the central canal, 
but could not show that they bore any relation to the scar 
formation. Barr, Dawson and Marsnatt (1) (1899) report 
some careful experiments on dogs, which led them to believe, 
on the basis of physiological evidence, that the dorsal root 
fibers, which they had previously destroyed, had re-established 
