TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 135 



Movements of the limb were practically normal. The shoulder 

 and limb muscles were completely differentiated and were well 

 supplied by nerve fibers from the ventral rami of the second, 

 third, and fourth spinal nerves (fig. 13). From this figure it is 

 seen that although the course of the proximal portions of the 

 nerves is very similar to that of the normal limb nerves (fig. 4), 

 their distal portions are continued anteriorly for some distance 

 to the heterotopic limb. The ventral ramus of the second nerve 

 had no connection with that of the first and passed directly to 

 the brachial plexus. The ventral ramus of the first nerve was 

 distributed to the fragmentary m. sternohyoideus, the anterior 

 portion of which was wanting, as were also the m. geniohyoideus 

 and the m. hyoglossus. 



In comparing the muscular differentiation and innervation of 

 this case with that of former and subsequent cases (table 3) in 

 which the limb developed in the region of the gills, it is seen that 

 the immediate organic environment of the limb distinctly favors 

 more normal development. Cases in which the transplanted rudi- 

 ment remained in the gill region and there underwent differentia- 

 tion showed considerable deficiencies in the development of the 

 shoulder muscles as well as defective peripheral nerve connec- 

 tions (cases AA2Si5, 21, 25, etc., table 3). The large percentage 

 of defective limbs is likewise shown in table 1 B. The above 

 shows that even though the limb constitutes an equipotential, 

 self-differentiating system, the character of its development is 

 markedly affected by developmental potencies of the region into 

 which it is transplanted. Although the transplanted limb rudi- 

 ment possesses complete intrinsic potentialities to develop into 

 a normal appendage, it is clearly evident in these cases that the 

 high percentage of abnormalities in the gill region is due to an 

 inhibitory influence resulting from the more potent inherent 

 gill-producing properties of the tissues in the immediate organic 

 environment of the gills which offer a A'ery unfavorable environ- 

 ment for normal limb differentiation. The abnormahties on the 

 part of both gills and limb clearly show developmental conflicts 

 between the two systems. 



