AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, MARCH 30 



THE MORPHOGENESIS OF THE THYREOID GLAND 

 IN SQUALUS ACANTHIAS 



E. H. NORRIS 



From the Institute of Anatomy, University of Minnesota 



TWENTY-THREE FIGURES 



CONTENTS 



1 . Introduction 187 



2. Material and methods 188 



3. Prefollicular period 190 



a. Organogenesis 190 



b. Histogenesis 192 



4. Follicular period 198 



5. Blood supply 204 



6. Discussion and conclusions 210 



7. Summary 216 



8. Literature cited 219 



1. INTRODUCTION 



The morphogenesis of the elasmobranch thyreoid presents 

 many problems of more than intrinsic interest and import, 

 because of their bearing upon the large number of researches 

 regarding the development and structure of this organ throughout 

 the vertebrate series. The thyreoid gland of this form shows with 

 almost diagrammatic clearness, in its earlier stages, a number of 

 features which are rendered relatively obscure in forms which are 

 more complex or undergo a more rapid development. The gland 

 further exhibits a number of characteristics, both during its early 

 development and during the follicular period, which are of 

 particular interest in the light of recent work on the human 

 thyreoid gland (Norris, '16). Moreover, the organ presents a 

 very fortunate field for a continued study of the relation of 

 parenchymatous and vascular structures. 



This study was undertaken in the Anatomical Laboratory of 

 the University of Minnesota at the suggestion of Prof. R. E. 

 Scammon, under whose supervision the work was conducted. 



187 



