Degree of Injury and Rate of Regeneration 557 
cussed in the present paper involves more than a proportional 
increase. 
The following general conclusion results naturally from the 
data as determined at present. The removal of a part of an 
animal involving a slight or moderate degree of injury ‘s followed 
by a rate of regeneration that is less than it is in case the removal 
is accompanied by an additional removal of slight or moderate 
amount in other parts of the animal. If the degree of injury in 
either case is considerable, the additional injury results in a 
decrease in rate of regeneration of the part. For every part cap- 
able of regeneration, the statement can therefore be madethat 
its rate of regeneration increases with increase in additional injury 
up to an optimum degree beyond which further injury causes a 
decrease in rate. 
In a purely descriptive way it may be said that the increase 
in rate reveals the presence of a kind of inertia in the body of 
the animal comparable to ordinary physical inertia. [he time 
necessary for the repair of an injury is not least in the case of 
the lowest injury but a certain degree of injury is necessary 
before the regenerative powers of the organism can work at their 
best. In the same way also in the case of the functional opercu- 
lum of a Serpulid worm a considerable degree of injury 1s neces- 
sary to start the process of reversal of the opercula. ‘The decrease 
in rate that follows at higher degrees of injury is undoubtedly 
due to another factor, the active disturbance of the ordinary 
mechanism of the body. 
SUMMARY 
1 An attempt was made to determine the pure effect of the 
degree of injury to the individual upon the rate of regeneration 
of a removed part. 
2 The principal method consisted of the comparison of the 
rates of regeneration of an organ removed at a constant level 
when other parts of the animal were or were not removed at 
the same time. 
3 A special study was made of the various other factors influ- 
