ENVIRONMENT AND REGENERATION 481 



the regeneration curves being plotted with abscissa as time and 

 the COo production curves being plotted with per cent of normal 

 CO2 production and CO2 produced per gram of tadpole as 

 abscissa, they do serve to show that as CO2 production is increased, 

 regeneration is decreased progressively. Similar results were 

 obtained in experiments in which the base used was Ca(0H)2. 

 Figure 10 shows the regeneration of these tadpoles. Figure 12 

 shows the CO2 production expressed as per cent of normal CO2 

 produced in distilled water (dotted line) and the time required 

 to regenerate 15 and 20 per cent of the amount removed. 



Child ('13) has shown that for Planaria the rate of regenera- 

 tion is correlated with rate of oxygen metabolism, and that 

 worms or pieces of worms having high rates of CO2 production 

 regenerate more rapidly than those having lower rates of CO2 

 production. The above experiments upon tadpoles show that 

 a rise in CO2 production due to the basicity of the medium 

 is correlated with a decrease in regeneration. The apparent 

 discrepancy between these two statements disappears upon con- 

 sidering that the Planaria used by Child were all under optimum 

 conditions for regeneration and growth, but differed only in 

 size and physiological age; whereas of the tadpoles, which were 

 of as nearly as possible the same size and physiological age, only 

 the controls were under optimum conditions for regeneration. 

 Although in case of normal individuals under optimum con- 

 ditions a rapid oxygen metabolism is often correlated with rapid 

 growth, it is a matter of common knowledge that under certain 

 conditions as a wasting fever or excessive muscular exertion 



the amount of CO2 produced per gram of body weight, there is an increase with 

 increased concentration of KOH and accompanying a retarded regeneration in 

 the higher concentrations. 



Fig. 12 Graph showing regeneration (solid lines) and CO2 production as com- 

 pared to the normal (dotted line) in increasing concentrations of Ca(0H)2 of 

 tadpoles whose regeneration is shown in figure 10. Ordinate, cc. O.OIN Ca(0H)2 

 in 400 cc. of solution; abscissa for per cent regenerated, time in days, for per cent 

 CO1 produced, per cent of normal CO2 production in distilled water; numbers at 

 ends of solid lines, per cent regenerated. As in figure 11, there is an increase in 

 CO-i production and decrease in regeneration with increased concentration of the 

 base. 



