THE PIGMENTARY, GROWTH AND ENDOCRINE 



DISTURBANCES INDUCED IN THE ANURAN 



TADPOLE BY THE EARLY ABLATION 



OF THE PARS BUCCALIS OF 



THE HYPOPHYSIS 1 



1. INTRODUCTION 



Only within the brief period of four years has the favorable 

 character of the early amphibian tadpole for analyzing the func- 

 tional nature and the reactions of the members of the endocrine 

 system been recognized. This may indeed seem strange, since 

 the value of this material, to which attention was called by 

 Born and which has been used so advantageously by Har- 

 rison, in the solution of those problems requiring experimental 

 procedure upon the early embryo has long been appreciated. 

 The early amphibian tadpole is peculiarly useful in experimental 

 biological investigations, since in its earliest stages it is avail- 

 able for operation and has the inherent capacity to survive 

 the most severe mutilations. These characteristics make a 

 special appeal in studies upon the functional interrelationships 

 obtaining in the endocrine system, for derangements in this 

 system can be induced by the ablation of certain of its members 

 in their early embryonal and non-functional stages by a simple 

 operation, in itself not harmful. The early removal of a gland 

 will afford then knowledge not only of the essentiality of this 

 gland per se, but also concerning the dependence of the other 

 endocrine organs upon this gland for their full development. 

 This interdependence may be productive of even greater struc- 

 tural changes in the other glands than a later operation would 

 produce, because of the lability inherent in embryonal structures. 

 Further, the utilization of embryonal material would appear 



1 Aided by a grant from the Research Board of the University of California. 



