118 Cc. V. MORRILL 
down, liberating the cells which again become active and form 
new matrix. In this case, however, the cells do not dedifferenti- 
ate so far as to become indifferent; they remain cartilage forming 
cells. The formation of the peripheral cartilage and that part 
of the axial cartilage derived from endosteal cells is of course 
quite different in nature. Here the more or less undifferentiated 
cells of the periosteum and endosteum which have lain @ormant, 
are suddenly stimulated to activity by the amputation. They 
form cartilage first and later a portion of the cartilage is trans- 
formed into bone as described on page 115. 
It was stated at the beginning of this account that some animals 
were allowed to complete their regeneration to determine whether 
the new skeleton was like the old. There seems to be no dif- 
ference whatever provided sufficient time is allowed for devel- 
opment. Externally, a slight deformity sometimes appears at 
first, since the new bud does not always lie in the longitudinal 
axis of the limb. This is more common after operations at the 
knee-joint than at the hip-joint. In the course of time this 
irregularity disappears and tbe limb becomes normal in shape 
and position. Complete ossification, however, may take almost 
a year and sometimes even longer. 
A glance over the literature of regeneration in amphibia shows 
that the power to regererate a new normal skeleton does not 
extend to all animals of this class. Morgan (’03) found that in 
Amphiuma the new skeleton was abnormal and deficient al- 
though some specimens were kept under observation for nearly 
a year. Certain results which were obtained by the earlier 
experimenters Goette and Fraisse seem to indicate that some of 
the European urodeles (Triton marmoratus and. Proteus) lack 
the power of complete regeneration but Kammerer (’06) states 
that this is not the case if the animals are kept under favorable 
conditions and for a sufficient length of time. 
In the Anura the power is much more limited. New limbs will 
regenerate only if amputation is made in the tadpole stage. 
Barfurth (’94) was the first to find that the limbs of frog-larvae 
(Rana fusea) are capable of regeneration, but this power disap- 
pears in the progress of development. Ridewood (’98) obtained 
