534 S. WALTER RANSON 
2. The attempts to obtain regeneration in a peripheral stump 
permanently separated from the spinal cord and spinal ganglia 
have led to negative results. So great is the regenerative energy 
of the central stump in young animals that the new axons to 
which it gives rise may bridge very great gaps to reach the dis- 
tal stump; and new axons may grow into that stump from other 
nerves. Bethe’s elaborate precautions to prevent such union 
have clearly not been adequate, as is shown by the experiments 
of Langley and Anderson (’04) and Lugaro (’05). Nothing 
short of the complete removal of the entire lumbo-sacral spinal 
cord with the associated spinal ganglia can be regarded as effec- 
tually preventing such reunion and these experiments have 
been negative. Since, however, such experiments are open 
to the objection that the high grade of marasmus caused by 
such an operation could in itself be sufficient to account for 
negative results, no very valuable evidence is likely to be fur- 
nished by this line of experimentation. Since we now have, 
in the Cajal method, a technique which enables us to see clearly 
how regeneration occurs when the two ends of the nerve are 
allowed to unite, there ceases to be any reason for attempting 
to secure an isolated stump. It is highly improbable that there 
would occur in such an isolated stump a process essentially dif- 
ferent from that which occurs when the two ends are allowed 
to unite. 
3. It can be shown by the Cajal stain that the axons of both 
medullated and non-medullated fibers in the central stump 
give rise to a large number of branches which make their way 
through the scar and enter the protoplasmic bands, which they 
utilize as pathways toward the periphery. Perroncito, Mari- 
nesco and Cajal have reached these same conclusions on facts 
similar to those presented in the preceding sections of this paper. 
Poscharissky, whose observations agree with those of the others, 
hesitates to draw any conclusions. The facts upon which the 
conclusions just mentioned are based have already been sum- 
marized under the heading “The mechanism of the regener- 
ation of nerves.” 
