158 S. R. DETWILER 
certain degree somewhat less developed qualitatively as is seen 
by an examination of table 3. This would naturally account 
for considerable deficiencies of movement, yet by an examination 
of individual cases it is found that the degree of motion is not 
directly correlated with the number of muscles innervated, nor 
with the number of segments contributing nerve fibers. For 
example, case AS4.; with only four of the nine muscles innervated 
showed a considerable degree of shoulder movement. In case 
AS5.; with an equal number of muscles innervated (table 3), 
there was practically no shoulder movement. The same was 
true in case AS5o¢. 
Further evidence which shows that the completeness of shoul- 
der movement is not entirely dependent upon the number of 
muscles innervated is afforded by an examination of homoplastic 
limbs transplanted the distance of four and five segments pos- 
terior to the normal intact limb of the host. For example, in 
case HS5. (fig. 22) all of the shoulder muscles received nerve 
fibers, yet practically no function was observed. 
That the degree of function of the limbs cannot be a result 
of the number of segments supplying nerves to the brachial 
plexus is also shown by the fact that the function of the limbs is 
more complete in some cases where only three segmental nerves 
contribute to the plexus than in others where four nerves are 
involved, even though the number of shoulder muscles innervated 
in both cases is the same. Of course, the number of segmental 
nerves contributing to the brachial plexus is not as important as 
the actual number of nerve fibers entering the shoulder muscles 
and the limb. However, it is practically impossible to count 
the number of nerve fibers in a given segmental nerve, since in 
larvae of the age studied the fibers are non-myelinated and can- 
not be counted with any degree of accuracy. Although the 
segmental nerves contributing to the innervation of the trans- 
planted limb were larger than their counterparts which do not 
supply a corresponding end organ, the increase in size was found 
to be the result of a hyperplasia of the peripheral afferent neu- 
rones, there being no positive evidence that the functional activity 
of the transplanted limb had brought about any definite hyper- 
plasia of the somatic motor neurones. 
