AiSriMAL COLLAGENASE AND COLLAGEN METABOLISM 



683 



20 30 40 50 



HOURS OF INCUBA TION 

 Fig. 12. Collagenolytic activity of tadpole tail fin in culture on radioactive 

 collagen gels at 27°C. 



was fourfold greater than in the control group. In several other re- 

 peat experiments the increase in activity of the treated animal tissues 

 ranged from two to four times that of the controls. 



In a second experiment, groups of tadpoles were maintained in 

 a thyroxin-containing bath for inter\als ranging from 1 to 7 days. 

 Figure 13 illustrates collagenohtic activity in tail fin and back skin 

 along with the decrement in tail length. The direct relationship of 



