DEGENERATION AND REGENERATION OF NERVE FIBERS 493 
of these bands into axial strands and granular sheaths ‘Achsial- 
strangfasern’; (3) appearance of fibrils in the axial strands in 
the neighborhood of the nuclei; (4) fusion of these discontin- 
uously formed fibrils: into fibrillar bands; (5) discontinuous 
formation of a myelin sheath. Bethe maintains that such 
transformation can occur only in young animals and even then 
only in a limited number of the fibers. Many fibers in young 
animals and all in adult animals are incapable of developing 
beyond the stage of protoplasmic bands without some stimulus 
from the central stump. 
So convincing did these experiments of Bethe appear that 
they excited the greatest interest and have led to many at- 
tempts to secure confirmation of his results. Miimnzer (’02), 
Head and Ham (’03) and Mott, Halliburton and Edmunds 
(04) presented evidence to show that all new axons in the periph- 
eral stump were outgrowths from the old axons of the central 
end. But there have appeared two investigations, those of 
Langley and Anderson (’04) and Lugaro (’05), which not only 
show that Bethe’s conclusions were wrong, but show clearly 
the fallacies upon which his erroneous conclusions were based. 
The work of Langley and Anderson (’04) was carried out on 
kittens and young rabbits. Experiment 5 is typical of their 
results. The right sciatic nerve was cut high up in the thigh, 
turned down and sewed into the skin above the knee. After 
251 days the sciatic was cut above the first point of section 
and the femoral nerve was cut near the inguinal ligament. The 
peripheral sciatic stump, twelve days after the second operation, 
contained no sound medullated fibers but many degenerated 
ones. Summing up all their experiments they say: 
We find that all the medullated nerve fibers, which reform in the 
peripheral end of a nerve, degenerate when the nerves which run to 
the tissues near the cut end are cut near the spinal cord; in other words, 
in our experiments all medullated fibers in the peripheral ends of the 
cut nerves were fibers which had become connected with the central 
nervous system. If then, autogenetic regeneration of fibers had oc- 
curred, every one of them had become connected with the central end 
of some nerve fiber. On the autogenetic theory this seems to us in 
the highest degree unlikely. 
