Influence of the Nervous System 653 
There remains then the possibility that nerves from more cephalad 
regions might have innervated the limbs. ‘This seems altogether 
improbable for the following reasons. While we know nothing 
about the region anterior to the plexus in this case, in other animals 
to be mentioned shortly, the nerve cord was completely removed 
from one to five vertebrz anterior to the plexus, a distance sufh- 
ciently great to prevent altogether, or at least for a time, the growth 
of anterior fibers into the leg. Secondly, the greater portion of 
the nerve fibers do not degenerate till long after the new limb has 
appeared, i. e., the nerves of the leg exert no chemotactic influence 
upon the nerves in the more anterior regions. “Thirdly, it will also 
-be pointed out later that the presence of a very minute portion of 
the nerve cord in the plexus region gives some power of movement 
to the limbs. The total removal from the plexus and adjoining 
regions is always followed by complete and permanent paralysis 
of both limbs, so that the latter condition may betakento indicate 
the total absence of motor nerve innervation to the rear limbs. 
These facts may be interpreted in but one way, that the legs 
regenerated in the total absence of motor innervation. 
A brief account of some other cases will make clear several 
doubtful points and strengthen the conclusion already drawn. 
_ No. 1.34. Preserved fifty days after the operation. ‘The regen- 
erated limb was 2 mm. long, with four toes. No trace of the nerve 
cord was found beginning about 2 mm. anterior to the origin of the 
first plexus nerve and as far backwards as the amputated end 
of the tail. Other features are essentially the same as in No. 1.27 
except that degeneration of the nerve fibers had not proceeded as far. 
No. 5.3. This animal was also preserved fifty days after paral- 
ysis. It differed from No. 1.34 in that the limbs were first ampu- 
tated, and twenty-five days later the nerve cord was removed. 
The spinal column was cordless beginning about 2 mm. anterior 
to the plexus to the end of the tail inclusive. The legs however 
showed some important changes. Though seventy-five days had 
elapsed after its amputation, only 14 mm. had regenerated. Fig. | 
3 is a longitudinal median section ae the nerve between the knee 
and the amputatedend. Itisa typical picture of Wallerian degen- 
eration, in a rather advanced stage. Near the amputated end, 
