450 ROSS G. HARRISON 
eye. After the first embryo has been prepared, the ectoderm 
is removed from the limb region of another specimen, with as little 
injury as possible to the mesoderm, and the latter is cut out from 
below and behind the pronephros and transferred as a single piece 
to the pocket. It is often difficult to get this small mass of 
tissue inserted, because it is very sticky and is liable to be pulled 
out when the instrument is withdrawn. Having a small hole 
in the distal side of the pocket facilitates a deep insertion and 
consequently the retention of the transplanted cells. Healing 
of wounds of this character is rapid and without secondary 
complications. ‘The mesoderm cells are, however, rather loosely 
held together and a considerable amount of disintegration may 
oecur—more than when the limb bud is transplanted in toto. 
The results of the experiments were as follows: 
Embry odiedsnrematureliy:. 3c ety 2 tid: yo:0( 2 eahune ieiness Boa pee 4 
Resorption of transplanted tissues’. <q... . eters cia ne see Sere eee 5 
Small :nodule:developed/sa’ 5.7 fee ok Sea eee oO cee 36 
Long ‘appendage without digits, jsc0+css. sotto ae see eee ee 1 
Limb of approximately full size with digits, usually showing redupli- 
CRUTONO Ea clrcctecte rgd abe Re Oe olen: ote Se ee 6 
Total cars. 4 sfernsitia Sad csheuicaee isons dente ics Gus ve Rea RE Cee eee 19 
These results are not essentially different from those obtained 
when the whole limb bud is transplanted, except that the limbs 
which do develop when the mesoderm is taken alone are more 
likely to show deformities. This was to have been expected in 
view of the difficulties of handling the mesoderm without the 
firm ectodermal covering to hold it together. Since the indi- . 
vidual cases are of interest their histories will be presented 
separately. 
Experiment Tr. Mes. 1. May 9, 1912. Mesoderm from left limb 
bud transplanted to left side. Some oozing from wound three hours 
afterward, indicating loss of tissue. 
May 12. Small lump in region of graft. 
May 15. Transplanted limb is getting much longer and is not 
much below the normal one in size. 
May 18. Beginning to show digitations. 
May 21. Larva has marked spinal curvature, but seems otherwise 
