SYMMETRY IN TRANSPLANTED LIMBS 7 
not especially cleaned, there is no evidence, aside from certain 
exceptional cases, that the tissue of the wound bed displaces the 
transplanted bud, though the possibility of its participation in 
the make-up of the limb cannot be excluded, and it probably 
actually does take place to some extent. 
In transplanting the limb bud to a location other than the 
normal, the recipient embryo is first prepared as in the other 
experiments. A ^vound of proper size is made, usually in the 
flank just below the ventral border of the myotomes, and the bud 
grafted in the same manner as described above. In doing this 
it is well to avoid injury to the pronephric duct (p. 15). 
Three different factors regarding the placement of the limbs 
have been considered in these experiments, viz.: 1) location of 
the graft in the embryo; 2) the side of the body on which it is 
placed (whether the same from which it was taken or the oppo- 
site); and 3) orientation with respect to the cardinal points of 
the embryo. The experiments thus fall into eight categories, 
as follows (fig. 1) : 
A. Limb buds placed in abnormal location — heterotopic 
transplantation. 
1. On the same side of body as origin — homopleural (horn.). 
a. Dorsal border of limb bud dorsal with respect to embryo — 
dorsodorsal {dd.). 
b. Dorsal border of hmb bud ventral with respect to embryo — 
dorsoventral {dv.). 
2. On side of body opposite to origin — heteropleural {het.). 
a. Dorsal border of limb bud dorsal with respect to embryo — 
dorsodorsal (dd.), in which case the anteroposterior axis is reversed. 
h. Dorsal border of limb bud ^'^entral with respect to embryo — - 
dorsoventral (dv.), in which case the anterior and posterior points 
of the graft correspond, respectively, to those of the embryo. 
B. Limb bud placed in natural location — orthotopic trans- 
plantation. 
The several categories under this head as under A. 
According to the rules stated on page 4, two of the combina- 
tions (homopleural dorsodorsal and heteropeural dorsoventral) 
yield limbs which are of the same side of the body as that on 
