TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 15% 
situation are likely to be somewhat larger than those developing 
more posteriorly, a condition very likely due to the fact that 
in the former position there is more room for development. 
With the development of larger girdles, of course, there would 
be a corresponding development of larger muscles which would 
permit of slightly greater shoulder movements than in the more 
posterior positions where the shoulder-girdle is not quite so 
large; but the difference in the degree of function of the limbs 
could not be a result of this factor alone, for girdles developing 
the distance of four segments posterior to the normal position 
are no larger than those developing six segments posterior to it, 
yet the difference in the degree of function of the limbs in these 
two positions is considerable, as is shown in table 1 a. 
Another factor, which must be considered when dealing with 
function, is the differentiation of the shoulder muscles, since 
movements of the limbs cannot be perfectly performed unless 
shoulder-muscle differentiation is complete. A study of the cross- 
section anatomy of the shoulder region of the transplanted limbs 
shows that shoulder-muscle differentiation is no less complete 
in cases where the limbs are removed considerable distances 
than in those where they are only slightly removed from the 
normal situation. An examination of table 3 shows that no 
cases were found in which there was complete absence of any 
of the shoulder muscles that typically develop in the heterotopic 
position. So, in limbs transplanted considerable distances away 
from the normal position and which exhibit practically no func- 
tion, a skeletomuscular mechanism exists adequate for all move- 
ments of the arm on the shoulder; hence, it is necessary to look 
elsewhere for the factors governing function of the limbs. 
This brings up the third factor, that of peripheral efferent 
innervation to both limb and shoulder muscles, deficiencies in 
which would readily account for restricted movements. The 
result of this study shows that the peripheral innervation to 
shoulder and limb is somewhat less complete quantitatively 
when transplanted to the more posterior positions than in cases 
where the transplanted limb receives segmental nerves from all 
or only a portion of the normal limb level of the cord, and to a 
