SYMMETRY IN TRANSPLANTED LIMBS 11 
accordance with the outline presented above. The larger groups 
of experiments have been considered apart from each other, and 
each subgroup is treated in a special section. The peculiar fea- 
tures of each of the larger groups have been considered at the 
beginning, and the results of the experiments summarized sep- 
arately at the end of each main section. The more general 
questions are treated in the final chapter. 
It has been thought best to provide numerous illustrations in 
order to avoid lengthy descriptions. Since it was not possible 
to keep a complete pictorial history of each case, those were se- 
lected for drawing that promised typical or otherwise interesting 
results. Unfortunately, however, it was not always possible to 
predict what the outcome of an experiment would be, so that 
some important cases were not drawn in early stages, while 
others of less interest were.^ 
GENERAL FEATURES OF THE DEVELOPMENT OF THE 
TRANSPLANTED BUDS 
The development of the transplanted limb buds must now be 
considered in comparison with normal development. When the 
normal limb bud appears it is a round prominence just below the 
pronephros. It soon becomes more sharply marked ofT from the 
background and begins to 'point' dorsoposteriorly.* The radial 
border of the fore arm and hand is at first ventrolateral, then ven- 
tral, and the first digits to arise are the first and second. The 
third and fourth digits appear later on the dorsal border of the 
hand, so that there is never any difficulty in distinguishing the 
ulnar from the radial border unless the third and fourth digits 
are entirely suppressed. The palmar surface of the hand faces 
at first ventromedially and later medially. 
The transplanted limbs, both heterotopic and orthotopic, 
give evidence of their orientation early in development, inasmuch 
' Almost all of the preliminary sketches and many of the finished drawings 
were made by Miss Lisbeth Krause. The former, which were pencil sketches, 
had to be redrawn for reproduction. For this part of the work and also for a 
number of the original drawings I am indebted to Mr. A. Hemberger and Mr. H. 
D. Rhynedance. 
8 Harrison, 'IS, p. 419. 
