REGENERATION AFTER EXARTICULATION 1A 
a solid mass of cartilage united to the femoral epiphysis (Hp./.) 
by a capsule with joint cavity (J.c.n.) as before. Distally it is 
in contact with a tarsal cartilage (7.c.) but no joint capsule has 
developed. The two portions of the new element are continu- 
ous proximally when traced through the series. Unfortunately 
intermediate stages in the formation of the new skeletal element 
were not obtained. The epiphysis of the femur (fig. 6, Hp./.) 
has the appearance of new cartilage similar to that of the new 
element (L.s.n.). This seems to indicate that the regeneration 
was centrifugal in direction and probably occurred in the same 
manner as described in the first section of this paper. No 
changes were observed in the tarsal cartilages. 
Figure 7 is from another specimen killed after one year and 
cut in a plane passing through the borders of the limb. The 
new elements here consist of two large masses of cartilage (L.s.n.) 
united by fibrous tissue and connected with femoral epiphysis 
(Kp.f.) by a capsule containing a joint cavity (J.c.n.).  Distally 
the new cartilages fall short of the tarsus. The tarsal cartilages 
themselves (7.c.) show signs of growth in a proximal direction 
(centripetal regeneration). They have become united proximally 
by a mass of cartilage which, however, has no connection with 
the new skeletal elements. The arrangement produces what 
may be called a soft joint. 
Other specimens in this experiment showed the formation of 
irregular masses or nodules of cartilage but not so extensively 
as the two described above. There appears, then, to be a limit 
to the power of regeneration under the conditions of the experi- 
ment. This may be due to an inhibiting influence from the 
presence of the foot and to shortening of the limb which leaves 
very little room for the new growth. It may be well to state 
that as soon as the wound heals, the animal uses the limb con- 
stantly when creeping over the bottom of the aquarium. Wendel- 
stadt (01) performed a similar experiment upon the anterior 
limb of the Axolotl but with entirely negative results though 
he kept the animals under observation for ten to fifteen months. 
The limbs shortened as in the case of Diemyctylus but the animals 
apparently made no attempt to use them. It is Just possible 
