120 Cc. V. MORRILL 
cified fibrous tissue or bone in the place occupied by the. old 
fibula. This mass may have developed from fragments of the 
old fibular epiphysis which were accidentally left in the wound 
in two of the operations.® 
The results of experiments 1 and 2 substantiate the conclusion 
of Wendelstadt and Reed that regeneration in a lateral direction 
(in the hmb) does not occur. 
Experiment 3. Hxtirpation of both leg bones and a portion of 
the femoral epiphysis but without injury to the tarsus. Number 
of animals, five:—Considerable shortening occurred but in no 
case did the foot drop off. One was killed after sixty-three days 
and the remainder after one year. Two of the latter showed some 
indication of regeneration. In these there were one or two car- 
tilaginous nodules, in one case fairly extensive, connected with 
the femoral epiphysis by fibrous tissue. The femoral epiphysis 
itself was restored in all. 
Experiment 4. Haxtirpation of both leg bones but without injury 
to either femoral epiphysis or tarsus. Number of animals, seven:— 
Shortening of course occurred. Two lost the foot subsequently 
and were discarded. Of the five remaining, one was killed at 
sixty days and the remainder after one year. All showed def- 
inite attempts at regeneration, in some cases quite well marked. 
Figures 5 and 6 from the same specimen cut in the dorsi-ventral 
plane show the extent of regeneration in the best marked case. 
The time elapsed was sixty days. Only a small portion of the 
femoral epiphysis (Hp.f.) and one tarsal cartilage (7’.c.) appear 
in figure 5, since the section lies near the border of the limb. 
The new skeletal element of the leg (L.s.n.) consists of an epi- 
physeal portion which articulates with the femur and a long, 
narrow bar of cartilage which is partly overlaid by bone at either 
end. (The bone is darkly shaded in the figure.) At the proxi- 
mal end a distinct joint capsule with cavity (J.c.n.) has developed. 
Figure 6, from a section near the median plane, shows another 
portion of the new skeletal element (L.s.n.).. This portion is 
8 In the experiments described in part II, all bones removed were examined 
under a binocular microscope to determine whether any part of them had been 
accidently left in the wound. 
