axjthok'8 abstract op this paper issued 

 by the bibliographic service, january 16 



THE EFFECT OF TRANSPLANTING A PORTION OF THE 



NEURAL TUBE OF AMBLYSTOMA TO A POSITION 



AT RIGHT ANGLES TO THE NORMAL 



H. L. WIEMAN 

 Zoological Laboratory, University of Cincinnati 



EIGHTEEN FIGURES 

 I 



It has been known for a long time that when the amphibian 

 spinal cord is severed, in early embryonic stages, restoration of 

 anatomical and physiological continuity takes place (Born, '97; 

 Harrison, '98; Hooker, '15). It is also known that when a section 

 of the cord is excised and replaced in a reverse anteroposterior 

 position, healing per primam occurs if the cut edges are care- 

 fully apposed (Harrison, '98, '03; Spemann, '12; Hooker, '15). 

 According to Hooker, the reversed section retains its original 

 morphological polarity, but its functional polarity becomes 

 reversed through adaptation. The nerve fibers show a marked 

 tendenc}^ to avoid entering the opposite wound surfaces. The 

 experiments I am about to describe were designed to test further 

 the regulative capacity of the amphibian neural tube. 



Eggs of Amblystoma punctatum were collected shortly after 

 deposition and allowed to develop in the laboratory. The stages 

 used for operation extended from the period of the fused neural 

 folds to a point just before the larva becomes sensitive, but most 

 of the operations were made in the earher stages. The operation 

 consisted in excising a piece of the neural tube and somites, equal 

 to the length of two somites, and replacing it, dorsal side up, 

 at right angles to its original position. Thus the axis of the 

 transplant formed an angle of 90° to the remainder of the neural 

 tube. The length of the transplant was made somewhat longer 

 than the width of the tube, in order to obtain a maximum length 



163 



