SOME EXPERIMENTS ON THE EFFECT OF AGE UPON 
THE RATE OF REGENERATION? 
BY 
CHARLES ZELENY 
INTRODUCTION AND GENERAL METHOD 
The experiments described in the present paper were under- 
taken with the object of determining the relation between the 
age of an animal and its rate of regeneration. ‘The general fact 
has been known since the time of Spallanzani that as a rule the 
regeneration of lost parts is not as rapid in old animals as in 
young ones.’ It is not, however, always clear whether by this 
is meant the total time necessary for the replacement of a removed 
part or the actual rate of proliferation of the new tissues. Further- 
more, exceptions to the general rule of decrease with age have 
been noted.3 
The data to be given were obtained as a part of the study of 
several of the factors controlling the rate of regeneration. They 
are imperfect in that there is no instance of the working out of 
the rate during a complete life history. A full discussion of the 
general methods employed and the elimination of sources of 
error is given in the introductions to the papers on successive 
regeneration and the effect of the degree of injury in this number 
of the Journal of Experimental Zoology. The statements made 
there are applicable to the present experiments and need not be 
repeated here. The individual catalogue numbers are given in 
1 Contributions from the Zodlogical Laboratory of Indiana University. No. 110. 
2 “Die Regenerationsfahigkeit nimmt mit zunehmendem Alter eines Tierexemplares ab.” Przibram, 
1909. Experimental-Zodlogie 2. Regeneration, p. 221. 
3 “Die scheinbare Unterbrechung auf mittleren Entwicklungsstadien in gewissen speziellen Fallen 
laszt sich auf den nachweislichen Wechsel in der Konsistenz oder der Gewebsverteilung zuriickfiihren.”” 
Przibram, 1909, l. c., p. 221. 
4 Successive Regenerations: additional observations and general discussion. This Journal. The 
effect of the degree of injury upon the rate of regeneration. This Journal. 
Tue JourNnaL or ExPERIMENTAL ZOGLOGY, VOL. VII, NO. 3. 
