682 A. F. Goldfarb 
and though all the controls regenerated tails 8 to 11 mm. long, 
not one of the operated animals developed a tail. ‘To make certain 
that lack of regeneration was not due to any peculiarity of the 
individuals, the tails of the operated animals were cut off a second 
time close to the former level, and new tails developed in the ordi- 
nary manner, and in the ordinary time. 
Cord and Skeleton Removed 
In another series of animals, both the cord and the major part 
of the skeletal axis were removed from the posterior two or three 
mm. Sometimes the end disintegrated down to the level where 
all the tissues were intact. [In some cases no sloughing or disinte- 
gration took place, as in the following examples. 
In No. 17.3 for instance there was no regeneration. ‘Time, 
77 days. Nocord and only small fragments of bone were found in 
the distal 2 mm. ‘The cap of embryonic tissue had formed as 
usual, but no further constructive changes were visible. 
In other animals of which 17.1 is an example, regeneration did 
take place. The operation was exactly the same as in the pre- 
ceding animals. In 17.1 the time was also 77 days. Yet a new 
cartilaginous axis and a new nerve cord had grown to the ampu- 
tated end and thence beyond to form a new tail g mm. long. In 
these cases it is very probable that not enough of the skeleton had 
been removed, so that they are essentially like those previously 
considered wherein less then 5 mm. of the nerve cord had been 
removed. 
Influence of Dorsal Ganglia in Regeneration 
There remains the possibility that the spinal ganglia may play an 
important role in regeneration. Some doubt may be expressed 
with regard to the influence or lack of influence of the dorsal gang- 
lia in the regeneration of the hind limbs. But with regard to the 
tail, it is perfectly clear that these ganglia exert no influence in 
regeneration. In those experiments where more than 5 mm. of 
the cord was destroyed, the ganglia were intact yet were unable to 
