156 S. R. DETWILER 
upon a number of factors outside the structure of the limb itself. 
Limbs transplanted only a short distance from the normal situ- 
ation have been found, in general, to grow slightly larger than 
those removed farther away; however, the degree of structural 
deficiency within the limb itself is not strictly proportional to 
the distance from its normal position. The limb being an 
equipotential system, it is to be expected that complete structural 
differentiation, exclusive of vascularization and innervation, 
should not be effected by location. 
All limbs classed in the category ‘normal limbs,’ which was 
based on purely topographic completeness, were also found to 
be for the most part structurally complete. Hence, it is seen 
that the gradual loss of function in limbs more remotely removed 
is In no wise the result of structural deficiencies. The gradual 
decrease, therefore, in the function of limbs as they become 
implanted more and more remote from the normal limb region 
suggests the following possible factors conditioning the degree 
of function: a) structural deficiencies in the shoulder-girdle; 
b) deficiencies in the shoulder musculature; c) the failure of certain 
shoulder muscles to receive innervation, and, d) the absence 
of proper central neurone connections. 
In a typical limb-bud transplantation the major portion of 
the shoulder-girdle rudiment is included. Since it is difficult 
to excise and transplant always exactly the same region of 
mesoderm and since the girdle rudiment in Amblystoma con- 
stitutes a mosaic (Detwiler, 718), there is considerable variation 
in the degree of its development in the heterotopic position. 
Yet its development, in general, is no less complete in cases 
where the limb has been removed a considerable distance from 
the normal situation than in those where it has been removed 
only a short distance. An examination of table 4 shows that 
the heterotopic girdles exhibit no specific deficiencies which can 
be correlated with the distance they have been transplanted 
from the normal situation. Hence, the gradual loss of function 
which the limbs exhibit as they are farther and farther removed 
cannot be the result of corresponding shoulder-girdle deficiencies. 
It is found, however, that girdles developing close to the normal 
