ENVIRONMENT AND REGENERATION 



489 



Fig. 17 Graph showing the regeneration of tadpoles in increasing concen- 

 trations of H2SO4. Each line, average regeneration of four tadpoles; dotted line, 

 controls; ordinate, per cent regenerated; abscissa, time in days; numbers at ends 

 of curves, cc. O.OLNH2SO4 in 200 cc. of solution. From data of table 5. 



Fig. 18 Graph showing retardation of regeneration of tadpoles in increasing 

 concentrations of H0SO4. Dotted lines, experimental data; solid lines, theoretical 

 curves; ordinate, concentration as cc. O.OIN H2SO4 in 200 cc. of solution; abscissa, 

 time in days; numbers on curves, per cent regenerated. From data of table 5. 

 These curves are comparable to those shown in figures 8, 11, 12, 14, and 16. 



Fig. 19 Graph comparing regeneration in increasing concentrations of acids. 

 Curve 1, H3PO4, 25 per cent regenerated; curve 2, H2SO4, 25 per cent regenerated; 

 curve 3, HNO3, 22.5 per cent regenerated; curve J^, HBr, 25 per cent regenerated. 

 Plotted as figure 18 from the same data as figures 6, 13, 15, and 17. The action of 

 HNO2, HBr, and H2SO4 is similar throughout. The acid action of H3PO4 seemed 

 to be obscured by its toxicity in higher concentrations. 



Fig. 20 Graph showing the CO2 production of tadpoles in increasing concen- 

 trations of HBr (curve 1) and HCl (curve 2). Ordinate, concentration as cc. 

 O.OIN acid in 400 cc. of solution; abscissa, per cent of normal CO2 produced in 

 distilled water. The regeneration of these tadpoles was progressively inhibited 

 as the concentration of acid increased. 



