/.«^" 
V 4/. . ./'' 
PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 1 NOVEMBER 15. 1915 Number 11 
EXPERIMENTS ON THE DEVELOPMENT OF THE LIMBS 
IN AMPHIBIA 
By Ross G. Harrison 
OSBORN ZOOLOGICAL LABORATORY, YALE UNIVERSITY 
Presented to the Academy, October 2.1915 
Although previous experiments by Barfurth/ Byrnes,^ Kammerer,^ 
Braus,^ Lewis^ and others have yielded many interesting facts regard- 
ing the development and regeneration of the limbs in Amphibia, the 
bounds of the limb rudiment at very early stages have not been deter- 
mined exactly in any species, and it is not known how wounds of a defi- 
nite size and character in the limb region affect the subsequent power to 
*se to a normal appendage. In order to control properly certain 
traL antation experiments upon the fore limbs in Ambly stoma, relating 
chieh^ to questions of position and laterality, it was, therefore, found 
necessary to determine first the regenerative power of the tissues of the 
limb region after the removal of the limb rudiment in whole or in part 
before differentiation had begun. Accordingly the following experi- 
ments were made: 
1. Simple extirpation of the body wall of the fore limb region at a 
period before the limb bud becomes visible on the surface, the size of 
the wound being varied. 
2. Extirpation of a definite portion of the limb region. 
3. Removal of the limb rudiment and subsequent covering of wound 
with ectoderm taken from some other region of the embryo. 
4. Removal of the mesoderm alone from the limb region, afterward 
replacing the overlying ectoderm. 
5. Removal of the ectoderm alone leaving the underlying mesoderm 
intact. 
539 
