426 
ROSS G. HARRISON 
TABLE 3 
Showing time factor for regeneration in the different classes of experiments 
CHARACTER OF OPERATION 
NUMBER 
OF CASES 
AVERAGE 
TIME AFTER 
OPERATION 
REGENER- 
ATION FIRST 
AVERAGE 
TIME AFTER 
OPERATION 
LAST 
PREVIOUS 
NUMBER OF 
CASES 
REGENER- 
ATION FIRST 
OBSERVED 
NUMBER OF 
CASES 
REGENER- 
ATION FIRST 
OBSERVED 
+ 
OLDEST 
STAGE 
NEGATIVE 
OBSERVA- 
TION 
FOLLOWED 
av 15 Days 
OR LATER 
AT 10 Days 
OR LATER 
OBSERVA- 
TION 
BY 
REGENER- 
ATION 
OBSERVED 
days days days 
Wound not covered: : 
Not cleaned...... 158 6.8 2.8 21 4 10 
@leaneds osiic32.. 19 9.2 5.4 if 2 15 
Wound covered: 
Not cleaned...... 2 ios Deon 1 1 4 
@leaned. 5.7.2 8 9.4 6.0 | 3 1 11 
* The figures in this class have no significance since in one of the two cases 
no observation was recorded between the fourth and the twenty-third day. 
e 
the older embryos in the not-cleaned series may be due to the 
fact that the limb bud can be lifted out more cleanly than in 
the younger stages, so that after-cleaning is less needed. The 
higher percentage of regeneration after operations in the older 
stages in the cases with cleaned wounds remains, however, 
anomalous. 
Delay in development after extirpation 
Removal of the limb rudiment, if it does not arrest develop- 
ment entirely, naturally retards it to a considerable degree, 
the delay being on the average greater in the case of the cleaned 
wounds than in the others (Table 3). In a few cases outward 
signs of regeneration were noted as early as four days after oper- 
ation, though usually not until later. Since it was not practica- 
ble to observe the embryos each day, it cannot be stated ex- 
actly when regeneration did begin in each case. One hundred 
and fifty-eight cases with ordinary wounds show that the re- 
generating limb was first noted on the average 6.8 days after 
the operation, the last previous observation having been made 
on the average at 2.8 days. In the case of the cleaned wounds, 
the first observation of regeneration averaged 9.2 days after 
operation, the last previous observation having been at 5.4 
