ZOOLOGY: S. R. DETWILER 
327 
The outgrowing third, fourth and fifth spinal nerves in Ambly stoma, 
effecting connection with the Hmb rudiment at a period when it occu- 
pies its maximum extent (anterior border of the third somite to the 
posterior border of the fifth), become converged into a plexus as a re- 
sult of concentration of the rudiment into the definitive limb bud which 
centers under the fourth myotome. Such convergence having taken 
place, a typical normal plexus as illustrated in figure 1 is produced. 
However, in the examination of the segmental nerve supply to the 
anterior limb when transplanted posteriorly through distances ranging 
from one to seven segments, it is found that limbs so placed receive the 
FIG. 1. GRAPHIC RECONSTRUCTION OF THE NORMAL LEFT BRACHIAL PLEXUS OF CASE 
AS426, PRESERVED SIXTY-EIGHT DAYS AFTER THE OPERATION. X 20 
bulk of their nerve components from spinal segments situated anterior 
to the implanted limb rudiment rather than from segments correspond- 
ing to the new position of the limb (table 2 and fig. 2) . 
As has been observed previously, a very significant feature of table 2 
illustrates the tendency of the transplanted limbs to be innervated by 
the nerves developing from the normal limb level of the cord, this 
tendency being most marked in the fourth and fifth nerves both of which, 
in the cases studied, were found to elongate in a postero-lateral direction 
a greater distance to effect innervation than did the third nerve or those 
developing from segments of the cord posterior to the normal limb 
level. 
Anterior limbs when implanted the distance of one or two seg- 
ments posterior to the normal position receive the normal segmental 
nerve contribution (table 2, series ASl and AS2). The function of such 
