278 LIMB F lELD OPERAT-IONS 



ROTATION OF THE LIMB AXES 



In these experlmenta it is necessary to mark the donor material in some way so that the 

 axes may be identified when the transplant is oriented in the host site. Generally this 

 may he accomplished in the normal course of excision where identifying marginal nicks may- 

 be used as identifying markers. Both anterior-posterior (A-P) and dorso-ventral (D-V) 

 axes are concerned. Use Urodele embryos of stage #29 or younger. 



a. Carefully cut out the ectoderm and the mesoderm of area "B" so that the bulk 

 of the limb area remains intact. Clean out the wound with a small hair loop, 

 removing all loose (white) mesodermal cells, and replace the excised mass of 

 tissue in the same wound area after making a l80° rotation of the graft, as in- 

 dicated by arrows in the accompanying diagrams (Fig. F) . Both axes will, in 

 this instance, be reversed. 



b. Remove ectoderm and mesoderm of area "B" from the right side of the donor and 

 orient it with the D-V axis still dorso-ventral but in the host wound area at 

 the region of the left limb anlage'. In this instance the A-P axis will be re- 

 versed. (Fig. A) 



c. Without disturbing the normal field of the host, transplant from other embryos 

 both areas listed above, similarly rotated (i.e., as in "a" and "b") but to the 

 locality of "X" on the hosts. In this manner a direct comparison may be made 

 with the hosts normal limb field. (See diagrams for various other possible 

 rotations of the two primary axes,) 



d. Bepeat the above rotational transplantations with older embryos, using Urodele 

 stages #55-#56, in order to determine whether there has been any further deter- 

 mination of axes within the limb field. 



These transplantations should be followed as long as the larvae can be maintained so 

 that the axial relations of the well developed limbs may be determined, and also to study 

 the degree of innervation of the transplanted limb. The control for these experlmenta 

 consists of excision and replacement without rotation of the limb field. 



EECORD OF BOTATION OF LIMB FIELD AXES 



