TEANSPLANTATION OF LIMBS IN AMBLYSTOMA 131 



the developing limb bud had rotated dorsally under the influence 

 of ectoderm dorsal to the limb, simulating a condition shown in 

 figure 6. It later assumed typical orientation and developed 

 into an appendage which, although somewhat small, was ex- 

 ternally normal in appearance (fig. 11). During later develop- 

 ment, the limb gradually shifted caudally so that its final position 

 was scarcely the distance of two segments anterior to the ortho- 

 topic position. Movements of the limb on the shoulder were 

 quite defective, owing to incomplete muscular differentiation 

 and imperfect innervation (table 3). The musculature of the 



Fig. 11 Ventral aspect of case AA2S21 drawn forty-eight days after the opera- 

 tion. Only one small external gill has developed, and the limb, which earlier 

 occupied the region of the second and third external gills (figs. 9 and 10) has 

 migrated caudally to its final position. X 5. 



limb itself was well differentiated and received innervation from 

 two nerve trunks (fig. 12), one on the flexor surface and the other 

 on the extensor surface. The shoulder-girdle was typical in 

 shape, although the ventral zone was much shorter than normal, 

 with a correspondingly curtailed development of the coraco- 

 brachial and the pectoral muscles. The limb and shoulder were 

 innervated by the ventral divisions of the second and third spinal 

 nerves (fig. 12). The distal portion of the latter, which contrib- 

 uted the main bulk of the nerve supply to the limb and the 

 shoulder had elongated a considerable distance anteriorly. The 

 ventral ramus of the second spinal nerve passed at first caudally 



