ANIMAL COLLAGENASE AND COLLAGEN METABOLISM 



677 



CONTROL 



THYROXIN Rx 



|.0*-X L 



HOURS AFTER PROLINE-H^ 



Fig. 9. Total activity of the three collagen fractions isolated from back skin 



does appear to be more rapid increase in the radioactivity of the 

 acid-extractable pool in metamorphosing tadpole back skin. 



In the back skin some resorption seems to be occurring, but at 

 a slower rate than in the tail fin. The higher rate of collagen forma- 

 tion in the back skin as compared with the tail fin ( Fig. 5 ) of resting 

 tadpoles is not altered by metamorphosis. This picture of the dif- 

 ferences between back skin and tail fin is consistent with the ob- 

 servations of thickening of the dermal layer of the body during 

 metamorphosis, associated with partial removal of the well ordered 

 basement lamella and its replacement by a new, less well ordered 

 terrestrial type of dermis ( Kemp, 1961 ) . 



Compared with the collagen distribution and turnover data from 

 other animal species such as rat (Harkness et al, 1954) and guinea 

 pig (Jackson, 1957; Jackson and Bentley, 1959), there are some 

 significant differences in the tadpole. In the rodent skin the insolu- 



